\input texinfo @c -*-texinfo-*-
@comment This is part of the netCDF documentation. See COPYRIGHT file
@c $Id: netcdf-f77.texi,v 1.72 2010/03/25 15:26:06 ed Exp $
@c %**start of header
@setfilename netcdf-f77.info
@setcontentsaftertitlepage
@settitle NetCDF Fortran 77 Interface Guide
@c Combine the variable, concept, and function indices.
@synindex vr cp
@synindex fn cp
@c %**end of header

@c version.texi is automatically generated by automake and contains
@c defined variables VERSION, UPDATED, UPDATED-MONTH.
@include version-f77.texi

@include defines.texi

@ifinfo
@dircategory netCDF scientific data format
@direntry
* netcdf-f77: (netcdf-f77).         @value{f77-man}
@end direntry
@end ifinfo

@titlepage
@title @value{f77-man}
@subtitle NetCDF Version @value{VERSION}
@subtitle @value{UPDATED-MONTH}
@author Russ Rew, Glenn Davis, Steve Emmerson, and Harvey Davies
@author Unidata Program Center


@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@ifnottex
@node Top, Use of the NetCDF Library, (dir), (dir)
@top @value{f77-man}

This document describes the FORTRAN-77 interface to the netCDF
library. This document applies to netCDF version @value{VERSION}. This
document was last updated in @value{UPDATED}.

For a complete description of the netCDF format and utilities see 
@ref{Top,, , netcdf, @value{n-man}}.

@end ifnottex

@menu
* Use of the NetCDF Library::   
* Datasets::                    
* Groups::                      
* Dimensions::                  
* User Defined Data Types::     
* Variables::                   
* Attributes::                  
* V2 FORTRAN Transition::       
* Summary of FORTRAN 77 Interface::  
* Combined Index::              

@detailmenu
 --- The Detailed Node Listing ---

Use of the NetCDF Library

* Creating a NetCDF Dataset::   
* Reading a NetCDF Dataset with Known Names::  
* Reading a netCDF Dataset with Unknown Names::  
* Adding New Dimensions::       
* Error Handling::              
* Compiling and Linking with the NetCDF Library::  

Datasets

* Datasets Introduction::       
* NetCDF Library Interface Descriptions::  
* NF_STRERROR::                 
* NF_INQ_LIBVERS::              Get netCDF library version
* NF_CREATE::                   
* NF__CREATE::                  
* NF_CREATE_PAR::               
* NF_OPEN::                     
* NF__OPEN::                    
* NF_OPEN_PAR::                 
* NF_REDEF::                    
* NF_ENDDEF::                   
* NF__ENDDEF::                  
* NF_CLOSE::                    
* NF_INQ Family::               Inquire about an Open NetCDF Dataset
* NF_SYNC::                     
* NF_ABORT::                    
* NF_SET_FILL::                 
* NF_SET_DEFAULT_FORMAT::       
* NF_SET_CHUNK_CACHE::          
* NF_GET_CHUNK_CACHE::          

Groups

* NF_INQ_NCID::                 
* NF_INQ_GRPS::                 
* NF_INQ_VARIDS::               
* NF_INQ_DIMIDS::               
* NF_INQ_GRPNAME_LEN::          
* NF_INQ_GRPNAME::              
* NF_INQ_GRPNAME_FULL::         
* NF_INQ_GRP_PARENT::           
* NF_INQ_GRP_NCID::             
* NF_INQ_GRP_FULL_NCID::        
* NF_DEF_GRP::                  

Dimensions

* Dimensions Introduction::     
* NF_DEF_DIM::                  
* NF_INQ_DIMID::                
* NF_INQ_DIM Family::           Inquire about a Dimension
* NF_RENAME_DIM::               

User Defined Data Types

* User Defined Types::          
* NF_INQ_TYPEIDS::              
* NF_INQ_TYPEID::               
* NF_INQ_TYPE::                 
* NF_INQ_USER_TYPE::            
* Compound Types::              
* Variable Length Array::       
* Opaque Type::                 
* Enum Type::                   

Compound Types Introduction

* NF_DEF_COMPOUND::             
* NF_INSERT_COMPOUND::          
* NF_INSERT_ARRAY_COMPOUND::    
* NF_INQ_COMPOUND::             
* NF_INQ_COMPOUND_FIELD::       

Variable Length Array Introduction

* NF_DEF_VLEN::                 
* NF_INQ_VLEN::                 
* NF_FREE_VLEN::                
* NF_PUT_VLEN_ELEMENT::         
* NF_GET_VLEN_ELEMENT::         

Opaque Type Introduction

* NF_DEF_OPAQUE::               
* NF_INQ_OPAQUE::               

Example

* NF_INQ_OPAQUE::               

Enum Type Introduction

* NF_DEF_ENUM::                 
* NF_INSERT_ENUM::              
* NF_INQ_ENUM::                 
* NF_INQ_ENUM_MEMBER::          
* NF_INQ_ENUM_IDENT::           

Variables

* Variables Introduction::      
* Variable Types::              
* NF_DEF_VAR::                  Create a Variable
* NF_DEF_VAR_CHUNKING::         
* NF_INQ_VAR_CHUNKING::         
* NF_SET_VAR_CHUNK_CACHE::      
* NF_GET_VAR_CHUNK_CACHE::      
* NF_DEF_VAR_FILL::             
* NF_INQ_VAR_FILL::             
* NF_DEF_VAR_DEFLATE::          
* NF_INQ_VAR_DEFLATE::          
* NF_INQ_VAR_SZIP::             
* NF_DEF_VAR_FLETCHER32::       
* NF_INQ_VAR_FLETCHER32::       
* NF_DEF_VAR_ENDIAN::           
* NF_INQ_VAR_ENDIAN::           
* NF_INQ_VARID::                
* NF_INQ_VAR family::           Get Information about a Variable from Its ID:
* NF_PUT_VAR1_  type::          
* NF_PUT_VAR_ type::            
* NF_PUT_VARA_ type::           
* NF_PUT_VARS_ type::           
* NF_PUT_VARM_ type::           
* NF_GET_VAR1_ type::           
* NF_GET_VAR_ type::            
* NF_GET_VARA_ type::           
* NF_GET_VARS_ type::           
* NF_GET_VARM_ type::           
* Reading and Writing Character String Values::  
* Fill Values::                 What's Written Where there's No Data?
* NF_RENAME_VAR::               
* NF_VAR_PAR_ACCESS::           

Attributes

* Attributes Introduction::     
* NF_PUT_ATT_ type::            Create an Attribute
* NF_INQ_ATT Family::           Get Information about an Attribute
* NF_GET_ATT_ type::            
* NF_COPY_ATT::                 
* NF_RENAME_ATT::               
* NF_DEL_ATT::                  

@end detailmenu
@end menu

@node Use of the NetCDF Library, Datasets, Top, Top
@chapter Use of the NetCDF Library

You can use the netCDF library without knowing about all of the netCDF
interface. If you are creating a netCDF dataset, only a handful of
routines are required to define the necessary dimensions, variables,
and attributes, and to write the data to the netCDF dataset. (Even
less are needed if you use the ncgen utility to create the dataset
before running a program using netCDF library calls to write
data. @xref{ncgen,,,netcdf, @value{n-man}}.)
Similarly, if you are writing software to access data stored in a
particular netCDF object, only a small subset of the netCDF library is
required to open the netCDF dataset and access the data. Authors of
generic applications that access arbitrary netCDF datasets need to be
familiar with more of the netCDF library.

In this chapter we provide templates of common sequences of netCDF
calls needed for common uses. For clarity we present only the names of
routines; omit declarations and error checking; omit the type-specific
suffixes of routine names for variables and attributes; indent
statements that are typically invoked multiple times; and use ... to
represent arbitrary sequences of other statements. Full parameter
lists are described in later chapters.

@menu
* Creating a NetCDF Dataset::   
* Reading a NetCDF Dataset with Known Names::  
* Reading a netCDF Dataset with Unknown Names::  
* Adding New Dimensions::       
* Error Handling::              
* Compiling and Linking with the NetCDF Library::  
@end menu

@node Creating a NetCDF Dataset, Reading a NetCDF Dataset with Known Names, Use of the NetCDF Library, Use of the NetCDF Library
@section Creating a NetCDF Dataset
@cindex creating dataset
@findex NF_CREATE, typical use
@findex NF_DEF_DIM, typical use
@findex NF_DEF_VAR, typical use
@findex NF_PUT_ATT, typical use
@findex NF_ENDDEF, typical use
@findex NF_PUT_VAR, typical use
@findex NF_CLOSE, typical use

Here is a typical sequence of netCDF calls used to create a new netCDF
dataset: 

@example
    NF_CREATE           ! create netCDF dataset: enter define mode
         ... 
       NF_DEF_DIM       ! define dimensions: from name and length
         ... 
       NF_DEF_VAR       ! define variables: from name, type, dims
         ... 
       NF_PUT_ATT       ! assign attribute values
         ... 
    NF_ENDDEF           ! end definitions: leave define mode
         ... 
       NF_PUT_VAR       ! provide values for variable
         ... 
    NF_CLOSE            ! close: save new netCDF dataset
@end example

Only one call is needed to create a netCDF dataset, at which point you
will be in the first of two netCDF modes. When accessing an open
netCDF dataset, it is either in define mode or data mode. In define
mode, you can create dimensions, variables, and new attributes, but
you cannot read or write variable data. In data mode, you can access
data and change existing attributes, but you are not permitted to
create new dimensions, variables, or attributes.

One call to NF_DEF_DIM is needed for each dimension
created. Similarly, one call to NF_DEF_VAR is needed for each variable
creation, and one call to a member of the NF_PUT_ATT family is needed
for each attribute defined and assigned a value. To leave define mode
and enter data mode, call NF_ENDDEF.

Once in data mode, you can add new data to variables, change old
values, and change values of existing attributes (so long as the
attribute changes do not require more storage space). Single values
may be written to a netCDF variable with one of the members of the
NF_PUT_VAR1 family, depending on what type of data you have to
write. All the values of a variable may be written at once with one of
the members of the NF_PUT_VAR family. Arrays or array cross-sections
of a variable may be written using members of the NF_PUT_VARA
family. Subsampled array sections may be written using members of the
NF_PUT_VARS family. Mapped array sections may be written using members
of the NF_PUT_VARM family. (Subsampled and mapped access are general
forms of data access that are explained later.)

Finally, you should explicitly close all netCDF datasets that have
been opened for writing by calling NF_CLOSE. By default, access to the
file system is buffered by the netCDF library. If a program terminates
abnormally with netCDF datasets open for writing, your most recent
modifications may be lost. This default buffering of data is disabled
by setting the NF_SHARE flag when opening the dataset. But even if
this flag is set, changes to attribute values or changes made in
define mode are not written out until NF_SYNC or NF_CLOSE is called.

@node Reading a NetCDF Dataset with Known Names, Reading a netCDF Dataset with Unknown Names, Creating a NetCDF Dataset, Use of the NetCDF Library
@section Reading a NetCDF Dataset with Known Names
@findex NF_INQ_DIMID, typical use
@findex NF_INQ_VARID, typical use
@findex NF_GET_ATT, typical use
@findex NF_GET_VAR, typical use
@cindex reading datasets with known names

Here we consider the case where you know the names of not only the
netCDF datasets, but also the names of their dimensions, variables,
and attributes. (Otherwise you would have to do "inquire" calls.) The
order of typical C calls to read data from those variables in a netCDF
dataset is:

@example
    NF_OPEN               ! open existing netCDF dataset
         ... 
       NF_INQ_DIMID       ! get dimension IDs
         ... 
       NF_INQ_VARID       ! get variable IDs
         ... 
       NF_GET_ATT         ! get attribute values
         ... 
       NF_GET_VAR         ! get values of variables
         ... 
    NF_CLOSE              ! close netCDF dataset
@end example

First, a single call opens the netCDF dataset, given the dataset name,
and returns a netCDF ID that is used to refer to the open netCDF
dataset in all subsequent calls.

Next, a call to NF_INQ_DIMID for each dimension of interest gets the
dimension ID from the dimension name. Similarly, each required
variable ID is determined from its name by a call to NF_INQ_VARID.Once
variable IDs are known, variable attribute values can be retrieved
using the netCDF ID, the variable ID, and the desired attribute name
as input to a member of the NF_GET_ATT family (typically
NF_GET_ATT_TEXT or NF_GET_ATT_DOUBLE) for each desired
attribute. Variable data values can be directly accessed from the
netCDF dataset with calls to members of the NF_GET_VAR1 family for
single values, the NF_GET_VAR family for entire variables, or various
other members of the NF_GET_VARA, NF_GET_VARS, or NF_GET_VARM families
for array, subsampled or mapped access.

Finally, the netCDF dataset is closed with NF_CLOSE. There is no need
to close a dataset open only for reading.

@node Reading a netCDF Dataset with Unknown Names, Adding New Dimensions, Reading a NetCDF Dataset with Known Names, Use of the NetCDF Library
@section Reading a netCDF Dataset with Unknown Names
@findex NF_INQ_ATTNAME, typical use
@findex NF_INQ, typical use
@cindex reading dataset with unknown names

It is possible to write programs (e.g., generic software) which do
such things as processing every variable, without needing to know in
advance the names of these variables. Similarly, the names of
dimensions and attributes may be unknown.

Names and other information about netCDF objects may be obtained from
netCDF datasets by calling inquire functions. These return information
about a whole netCDF dataset, a dimension, a variable, or an
attribute. The following template illustrates how they are used:

@example
    NF_OPEN                   ! open existing netCDF dataset
      ... 
    NF_INQ                    ! find out what is in it
         ... 
       NF_INQ_DIM             ! get dimension names, lengths
         ... 
       NF_INQ_VAR             ! get variable names, types, shapes
            ... 
          NF_INQ_ATTNAME      ! get attribute names
            ... 
          NF_INQ_ATT          ! get attribute values
            ... 
          NF_GET_ATT          ! get attribute values
            ... 
       NF_GET_VAR             ! get values of variables
         ... 
    NF_CLOSE                  ! close netCDF dataset
@end example

As in the previous example, a single call opens the existing netCDF
dataset, returning a netCDF ID. This netCDF ID is given to the NF_INQ
routine, which returns the number of dimensions, the number of
variables, the number of global attributes, and the ID of the
unlimited dimension, if there is one.

All the inquire functions are inexpensive to use and require no I/O,
since the information they provide is stored in memory when a netCDF
dataset is first opened.

Dimension IDs use consecutive integers, beginning at 1. Also
dimensions, once created, cannot be deleted. Therefore, knowing the
number of dimension IDs in a netCDF dataset means knowing all the
dimension IDs: they are the integers 1, 2, 3, ... up to the number of
dimensions. For each dimension ID, a call to the inquire function
NF_INQ_DIM returns the dimension name and length.

Variable IDs are also assigned from consecutive integers 1, 2, 3,
... up to the number of variables. These can be used in NF_INQ_VAR
calls to find out the names, types, shapes, and the number of
attributes assigned to each variable.

Once the number of attributes for a variable is known, successive
calls to NF_INQ_ATTNAME return the name for each attribute given the
netCDF ID, variable ID, and attribute number. Armed with the attribute
name, a call to NF_INQ_ATT returns its type and length. Given the type
and length, you can allocate enough space to hold the attribute
values. Then a call to a member of the NF_GET_ATT family returns the
attribute values.

Once the IDs and shapes of netCDF variables are known, data values can
be accessed by calling a member of the NF_GET_VAR1 family for single
values, or members of the NF_GET_VAR, NF_GET_VARA, NF_GET_VARS, or
NF_GET_VARM for various kinds of array access.

@node Adding New Dimensions, Error Handling, Reading a netCDF Dataset with Unknown Names, Use of the NetCDF Library
@section Adding New Dimensions, Variables, Attributes
@cindex dimensions, adding
@cindex variables, adding
@cindex attributes, adding

An existing netCDF dataset can be extensively altered. New dimensions,
variables, and attributes can be added or existing ones renamed, and
existing attributes can be deleted. Existing dimensions, variables,
and attributes can be renamed. The following code template lists a
typical sequence of calls to add new netCDF components to an existing
dataset:

@example
    NF_OPEN             ! open existing netCDF dataset
      ... 
    NF_REDEF            ! put it into define mode
        ... 
      NF_DEF_DIM        ! define additional dimensions (if any)
        ... 
      NF_DEF_VAR        ! define additional variables (if any)
        ... 
      NF_PUT_ATT        ! define other attributes (if any)
        ... 
    NF_ENDDEF           ! check definitions, leave define mode
        ... 
      NF_PUT_VAR        ! provide new variable values
        ... 
    NF_CLOSE            ! close netCDF dataset
@end example

A netCDF dataset is first opened by the NF_OPEN call. This call puts
the open dataset in data mode, which means existing data values can be
accessed and changed, existing attributes can be changed (so long as
they do not grow), but nothing can be added. To add new netCDF
dimensions, variables, or attributes you must enter define mode, by
calling NF_REDEF.In define mode, call NF_DEF_DIM to define new
dimensions, NF_DEF_VAR to define new variables, and a member of the
NF_PUT_ATT family to assign new attributes to variables or enlarge old
attributes.

You can leave define mode and reenter data mode, checking all the new
definitions for consistency and committing the changes to disk, by
calling NF_ENDDEF. If you do not wish to reenter data mode, just call
NF_CLOSE, which will have the effect of first calling NF_ENDDEF.

Until the NF_ENDDEF call, you may back out of all the redefinitions
made in define mode and restore the previous state of the netCDF
dataset by calling NF_ABORT. You may also use the NF_ABORT call to
restore the netCDF dataset to a consistent state if the call to
NF_ENDDEF fails. If you have called NF_CLOSE from definition mode and
the implied call to NF_ENDDEF fails, NF_ABORT will automatically be
called to close the netCDF dataset and leave it in its previous
consistent state (before you entered define mode).

At most one process should have a netCDF dataset open for writing at
one time. The library is designed to provide limited support for
multiple concurrent readers with one writer, via disciplined use of
the NF_SYNC function and the NF_SHARE flag. If a writer makes changes
in define mode, such as the addition of new variables, dimensions, or
attributes, some means external to the library is necessary to prevent
readers from making concurrent accesses and to inform readers to call
NF_SYNC before the next access.

@node Error Handling, Compiling and Linking with the NetCDF Library, Adding New Dimensions, Use of the NetCDF Library
@section Error Handling

The netCDF library provides the facilities needed to handle errors in
a flexible way. Each netCDF function returns an integer status
value. If the returned status value indicates an error, you may handle
it in any way desired, from printing an associated error message and
exiting to ignoring the error indication and proceeding (not
recommended!). For simplicity, the examples in this guide check the
error status and call a separate function to handle any errors.

The NF_STRERROR function is available to convert a returned integer
error status into an error message string.

Occasionally, low-level I/O errors may occur in a layer below the
netCDF library. For example, if a write operation causes you to exceed
disk quotas or to attempt to write to a device that is no longer
available, you may get an error from a layer below the netCDF library,
but the resulting write error will still be reflected in the returned
status value.

@node Compiling and Linking with the NetCDF Library,  , Error Handling, Use of the NetCDF Library
@section Compiling and Linking with the NetCDF Library
@cindex linking to netCDF library
@cindex compiling with netCDF library
@cindex nf-config

Details of how to compile and link a program that uses the netCDF C or
FORTRAN interfaces differ, depending on the operating system, the
available compilers, and where the netCDF library and include files
are installed. Nevertheless, we provide here examples of how to
compile and link a program that uses the netCDF library on a Unix
platform, so that you can adjust these examples to fit your
installation.

Every FORTRAN file that references netCDF functions or constants must
contain an appropriate INCLUDE statement before the first such
reference:

@example
INCLUDE 'netcdf.inc'
@end example

Unless the netcdf.inc file is installed in a standard directory where
the FORTRAN compiler always looks, you must use the -I option when
invoking the compiler, to specify a directory where netcdf.inc is
installed, for example:

@example
f77 -c -I/usr/local/include myprogram.f
@end example

Unless the netCDF library is installed in a standard directory where
the linker always looks, you must use the -L and -l options to link an
object file that uses the netCDF library. Since version 4.1.3, the
netCDF Fortran library (named `libnetcdff') is distinct from the
netCDF C library (named `libnetcdf'), but depends on it.  If it is
installed as a shared library, you need only use `-lnetcdff' to
specify the Fortran library for linking.

For example, if installed as a shared library, use something like:

@example
f77 -o myprogram myprogram.o -L/usr/local/lib -lnetcdff
@end example

If installed as a static library, you will at least need to mention
the netCDF C library and perhaps other libraries, such as hdf5 or
curl, depending on how the C library was built.  For example:

@example
f77 -o myprogram myprogram.o -L/usr/local/lib -lnetcdff -lnetcdf
@end example

Use of the nf-config utility program, installed as part of the
netcdf-fortran software, provides an easier way to compile and link,
without needing to know the details of where the library has been
installed, or whether it is installed as a shared or static library.

To see all the options for `nf-config', invoke it with the `--help'
argument. 

Here's an example of how you could use `nf-config' to compile and link
a Fortran program in one step:

@example
f77 myprogram.f -o myprogram `nf-config --fflags --flibs`
@end example

If it is installed on your system, you could also use the `pkg-config'
utility to compile and link Fortran programs with the netCDF
libraries.  This is especially useful in Makefiles, to insulate them
from changes to library versions and dependencies.  Here is an example
of how you could compile and link a Fortran program with netCDF
libraries using pkg-config:

@example
export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
f77 myprogram.f -o myprogram `pkg-config --cflags --libs netcdf-fortran`
@end example

where here `--cflags' means compiler flags and `libs' requests that
the approriate libraries be linked in.

@node Datasets, Groups, Use of the NetCDF Library, Top
@chapter Datasets

@menu
* Datasets Introduction::       
* NetCDF Library Interface Descriptions::  
* NF_STRERROR::                 
* NF_INQ_LIBVERS::              Get netCDF library version
* NF_CREATE::                   
* NF__CREATE::                  
* NF_CREATE_PAR::               
* NF_OPEN::                     
* NF__OPEN::                    
* NF_OPEN_PAR::                 
* NF_REDEF::                    
* NF_ENDDEF::                   
* NF__ENDDEF::                  
* NF_CLOSE::                    
* NF_INQ Family::               Inquire about an Open NetCDF Dataset
* NF_SYNC::                     
* NF_ABORT::                    
* NF_SET_FILL::                 
* NF_SET_DEFAULT_FORMAT::       
* NF_SET_CHUNK_CACHE::          
* NF_GET_CHUNK_CACHE::          
@end menu

@node Datasets Introduction, NetCDF Library Interface Descriptions, Datasets, Datasets
@section Datasets Introduction
@cindex datasets, introduction

This chapter presents the interfaces of the netCDF functions that deal
with a netCDF dataset or the whole netCDF library.

A netCDF dataset that has not yet been opened can only be referred to
by its dataset name. Once a netCDF dataset is opened, it is referred
to by a netCDF ID, which is a small nonnegative integer returned when
you create or open the dataset. A netCDF ID is much like a file
descriptor in C or a logical unit number in FORTRAN. In any single
program, the netCDF IDs of distinct open netCDF datasets are
distinct. A single netCDF dataset may be opened multiple times and
will then have multiple distinct netCDF IDs; however at most one of
the open instances of a single netCDF dataset should permit
writing. When an open netCDF dataset is closed, the ID is no longer
associated with a netCDF dataset.

Functions that deal with the netCDF library include:
@itemize

@item
Get version of library. 

@item
Get error message corresponding to a returned error code. 
@end itemize

The operations supported on a netCDF dataset as a single object are:
@itemize

@item
Create, given dataset name and whether to overwrite or not. 

@item
Open for access, given dataset name and read or write intent. 

@item
Put into define mode, to add dimensions, variables, or attributes.

@item
Take out of define mode, checking consistency of additions. 

@item
Close, writing to disk if required. 

@item
Inquire about the number of dimensions, number of variables, number of
global attributes, and ID of the unlimited dimension, if any.

@item
Synchronize to disk to make sure it is current. 

@item
Set and unset nofill mode for optimized sequential writes. 

@item
After a summary of conventions used in describing the netCDF
interfaces, the rest of this chapter presents a detailed description
of the interfaces for these operations.
@end itemize

@node NetCDF Library Interface Descriptions, NF_STRERROR, Datasets Introduction, Datasets
@section NetCDF Library Interface Descriptions
@cindex interface descriptions

Each interface description for a particular netCDF function in this
and later chapters contains:

@itemize

@item
a description of the purpose of the function; 

@item
a FORTRAN function prototype that presents the type and order of the formal
parameters to the function;

@item
a description of each formal parameter in the C interface; 

@item
a list of possible error conditions; and 

@item
an example of a FORTRAN program fragment calling the netCDF function (and
perhaps other netCDF functions).
@end itemize

The examples follow a simple convention for error handling, always
checking the error status returned from each netCDF function call and
calling a handle_error function in case an error was detected. For an
example of such a function, see Section 5.2 "Get error message
corresponding to error status: nf_strerror".

@node NF_STRERROR, NF_INQ_LIBVERS, NetCDF Library Interface Descriptions, Datasets
@section NF_STRERROR
@findex NF_STRERROR

The function NF_STRERROR returns a static reference to an error
message string corresponding to an integer netCDF error status or to a
system error number, presumably returned by a previous call to some
other netCDF function. The list of netCDF error status codes is
available in the appropriate include file for each language binding.

@heading Usage 
@example
CHARACTER*80 FUNCTION NF_STRERROR(INTEGER NCERR)
@end example

@table @code
@item NCERR
An error status that might have been returned from a previous call to
some netCDF function.
@end table

@heading Errors 

If you provide an invalid integer error status that does not
correspond to any netCDF error message or or to any system error
message (as understood by the system strerror function), NF_STRERROR
returns a string indicating that there is no such error status.

@heading Example 

Here is an example of a simple error handling function that uses
NF_STRERROR to print the error message corresponding to the netCDF
error status returned from any netCDF function call and then exit:

@example
INCLUDE 'netcdf.inc'
   ... 
SUBROUTINE HANDLE_ERR(STATUS)
INTEGER STATUS
IF (STATUS .NE. NF_NOERR) THEN
  PRINT *, NF_STRERROR(STATUS)
  STOP 'Stopped'
ENDIF
END
@end example

@node NF_INQ_LIBVERS, NF_CREATE, NF_STRERROR, Datasets
@section Get netCDF library version: NF_INQ_LIBVERS
@findex NF_INQ_LIBVERS

The function NF_INQ_LIBVERS returns a string identifying the version
of the netCDF library, and when it was built.

@heading Usage 
@example
CHARACTER*80 FUNCTION NF_INQ_LIBVERS()
@end example

@heading Errors 

This function takes no arguments, and thus no errors are possible in
its invocation.

@heading Example 

Here is an example using nf_inq_libvers to print the version of the
netCDF library with which the program is linked:

@example
INCLUDE 'netcdf.inc'
   ... 
PRINT *, NF_INQ_LIBVERS()
@end example

@node NF_CREATE, NF__CREATE, NF_INQ_LIBVERS, Datasets
@section NF_CREATE 
@findex NF_CREATE 

This function creates a new netCDF dataset, returning a netCDF ID that
can subsequently be used to refer to the netCDF dataset in other
netCDF function calls. The new netCDF dataset opened for write access
and placed in define mode, ready for you to add dimensions, variables,
and attributes.

A creation mode flag specifies whether to overwrite any existing
dataset with the same name and whether access to the dataset is
shared.

@heading Usage 

@example
INTEGER FUNCTION NF_CREATE (CHARACTER*(*) PATH, INTEGER CMODE, 
                            INTEGER ncid)
@end example

@table @code
@item PATH
The file name of the new netCDF dataset.
 
@item CMODE
The creation mode flag. The following flags are available:
NF_NOCLOBBER, NF_SHARE, NF_64BIT_OFFSET, NF_NETCDF4 and
NF_CLASSIC_MODEL.  You can combine the affect of multiple flags in a
single argument by using the bitwise OR operator.  For example, to
specify both NF_NOCLOBBER and NF_SHARE, you could provide the argument
OR(NF_NOCLOBBER, NF_SHARE).

A zero value (defined for convenience as NF_CLOBBER) specifies the
default behavior: overwrite any existing dataset with the same file
name and buffer and cache accesses for efficiency. The dataset will be
in netCDF classic format. @xref{NetCDF Classic Format Limitations,,,
netcdf, @value{n-man}}.

Setting NF_NOCLOBBER means you do not want to clobber (overwrite) an
existing dataset; an error (NF_EEXIST) is returned if the specified
dataset already exists.

The NF_SHARE flag is appropriate when one process may be writing the
dataset and one or more other processes reading the dataset
concurrently; it means that dataset accesses are not buffered and
caching is limited. Since the buffering scheme is optimized for
sequential access, programs that do not access data sequentially may
see some performance improvement by setting the NF_SHARE flag. This
only applied to classic and 64-bit offset format files.

Setting NF_64BIT_OFFSET causes netCDF to create a 64-bit offset format
file, instead of a netCDF classic format file. The 64-bit offset
format imposes far fewer restrictions on very large (i.e. over 2 GB)
data files. @xref{Large File Support,,, netcdf, @value{n-man}}.

Setting NF_NETCDF4 causes netCDF to create a netCDF-4/HDF5 format
file. Oring NF_CLASSIC_MODEL with NF_NETCDF4 causes the netCDF library
to create a netCDF-4/HDF5 data file, with the netCDF classic model
enforced - none of the new features of the netCDF-4 data model may be
usedin such a file, for example groups and user-defined types. 

@item ncid
Returned netCDF ID.
@end table

@heading Errors 
NF_CREATE returns the value NF_NOERR if no errors occurred. Possible
causes of errors include:
@itemize

@item
Passing a dataset name that includes a directory that does not exist.
@item
Specifying a dataset name of a file that exists and also specifying
NF_NOCLOBBER.
@item
Specifying a meaningless value for the creation mode.
@item
Attempting to create a netCDF dataset in a directory where you don't
have permission to create files.
@end itemize

@heading Example 

In this example we create a netCDF dataset named foo.nc; we want the
dataset to be created in the current directory only if a dataset with
that name does not already exist:

@example
INCLUDE 'netcdf.inc'
  ... 
INTEGER NCID, STATUS
... 
STATUS = NF_CREATE('foo.nc', NF_NOCLOBBER, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF__CREATE, NF_CREATE_PAR, NF_CREATE, Datasets
@section NF__CREATE 
@findex NF__CREATE 

This function is a variant of NF_CREATE, NF__CREATE (note the double
underscore) allows users to specify two tuning parameters for the
file that it is creating. These tuning parameters are not written to
the data file, they are only used for so long as the file remains open
after an NF__CREATE.

This function creates a new netCDF dataset, returning a netCDF ID that
can subsequently be used to refer to the netCDF dataset in other
netCDF function calls. The new netCDF dataset opened for write access
and placed in define mode, ready for you to add dimensions, variables,
and attributes.

A creation mode flag specifies whether to overwrite any existing
dataset with the same name and whether access to the dataset is
shared.

@heading Usage 

@example
INTEGER FUNCTION NF__CREATE (CHARACTER*(*) PATH, INTEGER CMODE, INTEGER INITIALSZ, 
                            INTEGER BUFRSIZEHINT, INTEGER ncid)
@end example

@table @code
@item PATH
The file name of the new netCDF dataset.
 
@item CMODE
The creation mode flag. The following flags are available:
NF_NOCLOBBER, NF_SHARE, NF_64BIT_OFFSET, NF_NETCDF4, and
NF_CLASSIC_MODEL.

Setting NF_NOCLOBBER means you do not want to clobber (overwrite) an
existing dataset; an error (NF_EEXIST) is returned if the specified
dataset already exists.

The NF_SHARE flag is appropriate when one process may be writing the
dataset and one or more other processes reading the dataset
concurrently; it means that dataset accesses are not buffered and
caching is limited. Since the buffering scheme is optimized for
sequential access, programs that do not access data sequentially may
see some performance improvement by setting the NF_SHARE flag. This
flag has no effect with netCDF-4/HDF5 files.

Setting NF_64BIT_OFFSET causes netCDF to create a 64-bit offset format
file, instead of a netCDF classic format file. The 64-bit offset
format imposes far fewer restrictions on very large (i.e. over 2 GB)
data files. @xref{Large File Support,,, netcdf, @value{n-man}}.

Setting NF_CLASSIC_MODEL causes netCDF to enforce the classic data
model in this file. (This only has effect for netCDF-4/HDF5 files, as
classic and 64-bit offset files always use the classic model.) When
used with NF_NETCDF4, this flag ensures that the resulting
netCDF-4/HDF5 file may never contain any new constructs from the
enhanced data model. That is, it cannot contain groups, user defined
types, multiple unlimited dimensions, or new atomic types. The
advantage of this restriction is that such files are guarenteed to
work with existing netCDF software.

A zero value (defined for convenience as NF_CLOBBER) specifies the
default behavior: overwrite any existing dataset with the same file
name and buffer and cache accesses for efficiency. The dataset will be
in netCDF classic format. @xref{NetCDF Classic Format Limitations,,,
netcdf, @value{n-man}}.

@item INITIALSZ
This parameter sets the initial size of the file at creation time.

@item BUFRSIZEHINT
The argument referenced by BUFRSIZEHINT controls a space versus time
tradeoff, memory allocated in the netcdf library versus number of system
calls.

Because of internal requirements, the value may not be set to exactly
the value requested. The actual value chosen is returned by reference.

Using the value NF_SIZEHINT_DEFAULT causes the library to choose a
default. How the system chooses the default depends on the system. On
many systems, the "preferred I/O block size" is available from the
stat() system call, struct stat member st_blksize. If this is
available it is used. Lacking that, twice the system pagesize is used.

Lacking a call to discover the system pagesize, we just set default
bufrsize to 8192.

The BUFRSIZE is a property of a given open netcdf descriptor
ncid, it is not a persistent property of the netcdf dataset.

@item ncid
Returned netCDF ID.
@end table

@heading Errors 
NF__CREATE returns the value NF_NOERR if no errors occurred. Possible
causes of errors include:
@itemize

@item
Passing a dataset name that includes a directory that does not exist.
@item
Specifying a dataset name of a file that exists and also specifying
NF_NOCLOBBER.
@item
Specifying a meaningless value for the creation mode.
@item
Attempting to create a netCDF dataset in a directory where you don't
have permission to create files.
@end itemize

@heading Example 

In this example we create a netCDF dataset named foo.nc; we want the
dataset to be created in the current directory only if a dataset with
that name does not already exist:

@example
INCLUDE 'netcdf.inc'
  ... 
INTEGER NCID, STATUS, INITIALSZ, BUFRSIZEHINT
... 
INITIALSZ = 2048
BUFRSIZEHINT = 1024
STATUS = NF__CREATE('foo.nc', NF_NOCLOBBER, INITIALSZ, BUFRSIZEHINT, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_CREATE_PAR, NF_OPEN, NF__CREATE, Datasets
@section NF_CREATE_PAR
@findex NF_CREATE_PAR

This function is a variant of nf_create, nf_create_par allows users to
open a file on a MPI/IO or MPI/Posix parallel file system.

The parallel parameters are not written to the data file, they are
only used for so long as the file remains open after an nf_create_par.

This function is only available if the netCDF library was built with
parallel I/O.

This function creates a new netCDF dataset, returning a netCDF ID that
can subsequently be used to refer to the netCDF dataset in other
netCDF function calls. The new netCDF dataset opened for write access
and placed in define mode, ready for you to add dimensions, variables,
and attributes.

When a netCDF-4 file is created for parallel access, independent
operations are the default. To use collective access on a variable,
@xref{NF_VAR_PAR_ACCESS}.

@heading Usage 

@example
INTEGER FUNCTION NF_CREATE_PAR(CHARACTER*(*) PATH, INTEGER CMODE, 
                               INTEGER MPI_COMM, INTEGER MPI_INFO, 
                               INTEGER ncid)
@end example

@table @code
@item PATH
The file name of the new netCDF dataset.
 
@item CMODE
The creation mode flag. The following flags are available:
NF_NOCLOBBER, NF_NETCDF4 and NF_CLASSIC_MODEL.  You can combine the
affect of multiple flags in a single argument by using the bitwise OR
operator.  For example, to specify both NF_NOCLOBBER and NF_NETCDF4, you
could provide the argument OR(NF_NOCLOBBER, NF_NETCDF4).

Setting NF_NETCDF4 causes netCDF to create a netCDF-4/HDF5 format
file. Oring NF_CLASSIC_MODEL with NF_NETCDF4 causes the netCDF library
to create a netCDF-4/HDF5 data file, with the netCDF classic model
enforced - none of the new features of the netCDF-4 data model may be
usedin such a file, for example groups and user-defined types. 

Only netCDF-4/HDF5 files may be used with parallel I/O.

@item MPI_COMM
The MPI communicator.

@item MPI_INFO
The MPI info.

@item ncid
Returned netCDF ID.

@end table

@heading Errors 
NF_CREATE returns the value NF_NOERR if no errors occurred. Possible
causes of errors include:
@itemize

@item
Passing a dataset name that includes a directory that does not exist.
@item
Specifying a dataset name of a file that exists and also specifying
NF_NOCLOBBER.
@item
Specifying a meaningless value for the creation mode.
@item
Attempting to create a netCDF dataset in a directory where you don't
have permission to create files.
@end itemize

@heading Example 
This example is from test program nf_test/ftst_parallel.F.

@example
!     Create the netCDF file. 
      mode_flag = IOR(nf_netcdf4, nf_classic_model) 
      retval = nf_create_par(FILE_NAME, mode_flag, MPI_COMM_WORLD, 
     $     MPI_INFO_NULL, ncid)
      if (retval .ne. nf_noerr) stop 2
@end example

@node NF_OPEN, NF__OPEN, NF_CREATE_PAR, Datasets
@section NF_OPEN 
@findex NF_OPEN 

The function NF_OPEN opens an existing netCDF dataset for access.

@heading Usage 

@example
INTEGER FUNCTION NF_OPEN(CHARACTER*(*) PATH, INTEGER OMODE, INTEGER ncid)
@end example

@table @code

@item PATH
File name for netCDF dataset to be opened.
This may be an OPeNDAP URL if DAP support is enabled.
 
@item OMODE
A zero value (or NF_NOWRITE) specifies: open the
dataset with read-only access, buffering and caching accesses for
efficiency.

Otherwise, the creation mode is NF_WRITE, NF_SHARE, or
OR(NF_WRITE, NF_SHARE). Setting the NF_WRITE flag opens the dataset with
read-write access. ("Writing" means any kind of change to the dataset,
including appending or changing data, adding or renaming dimensions,
variables, and attributes, or deleting attributes.) The NF_SHARE flag
is appropriate when one process may be writing the dataset and one or
more other processes reading the dataset concurrently; it means that
dataset accesses are not buffered and caching is limited. Since the
buffering scheme is optimized for sequential access, programs that do
not access data sequentially may see some performance improvement by
setting the NF_SHARE flag.

@item ncid
Returned netCDF ID.
@end table

@heading Errors 

NF_OPEN returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
The specified netCDF dataset does not exist. 
@item
A meaningless mode was specified. 
@end itemize

@heading Example 
Here is an example using NF_OPEN to open an existing netCDF dataset
named foo.nc for read-only, non-shared access:

@example
INCLUDE 'netcdf.inc'
 ... 
INTEGER NCID, STATUS
... 
STATUS = NF_OPEN('foo.nc', 0, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF__OPEN, NF_OPEN_PAR, NF_OPEN, Datasets
@section NF__OPEN 
@findex NF__OPEN 

The function NF)_OPEN opens an existing netCDF dataset for access,
with a performance tuning parameter.

@heading Usage 

@example
INTEGER FUNCTION NF__OPEN(CHARACTER*(*) PATH, INTEGER OMODE, INTEGER
BUFRSIZEHINT, INTEGER ncid)
@end example

@table @code

@item PATH
File name for netCDF dataset to be opened.
 
@item OMODE
A zero value (or NF_NOWRITE) specifies: open the
dataset with read-only access, buffering and caching accesses for
efficiency

Otherwise, the creation mode is NF_WRITE, NF_SHARE, or
OR(NF_WRITE,NF_SHARE). Setting the NF_WRITE flag opens the dataset with
read-write access. ("Writing" means any kind of change to the dataset,
including appending or changing data, adding or renaming dimensions,
variables, and attributes, or deleting attributes.) The NF_SHARE flag
is appropriate when one process may be writing the dataset and one or
more other processes reading the dataset concurrently; it means that
dataset accesses are not buffered and caching is limited. Since the
buffering scheme is optimized for sequential access, programs that do
not access data sequentially may see some performance improvement by
setting the NF_SHARE flag.
 
@item BUFRSIZEHINT
This argument controls a space versus time tradeoff, memory allocated
in the netcdf library versus number of system calls.

Because of internal requirements, the value may not be set to exactly
the value requested. The actual value chosen is returned by reference.

Using the value NF_SIZEHINT_DEFAULT causes the library to choose a
default. How the system chooses the default depends on the system. On
many systems, the "preferred I/O block size" is available from the
stat() system call, struct stat member st_blksize. If this is
available it is used. Lacking that, twice the system pagesize is used.

Lacking a call to discover the system pagesize, we just set default
bufrsize to 8192.

The bufrsize is a property of a given open netcdf descriptor
ncid, it is not a persistent property of the netcdf dataset.

@item ncid
Returned netCDF ID.
@end table

@heading Errors 

NF__OPEN returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
The specified netCDF dataset does not exist. 
@item
A meaningless mode was specified. 
@end itemize

@heading Example 
Here is an example using NF__OPEN to open an existing netCDF dataset
named foo.nc for read-only, non-shared access:

@example
INCLUDE 'netcdf.inc'
 ... 
INTEGER NCID, STATUS, BUFRSIZEHINT
... 
BUFRSIZEHINT = 1024
STATUS = NF_OPEN('foo.nc', 0, BUFRSIZEHINT, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_OPEN_PAR, NF_REDEF, NF__OPEN, Datasets
@section NF_OPEN_PAR 
@findex NF_OPEN_PAR

This function opens a netCDF-4 dataset for parallel access.

This function is only available if the netCDF library was built with a
HDF5 library for which --enable-parallel was used, and which was
linked (like HDF5) to MPI libraries.

This opens the file using either MPI-IO or MPI-POSIX. The file must be
a netCDF-4 file. (That is, it must have been created using NF_NETCDF4
in the creation mode).

This function is only available if netCDF-4 was build with a version
of the HDF5 library which was built with --enable-parallel.

Before either HDF5 or netCDF-4 can be installed with support for
parallel programming, and MPI layer must also be installed on the
machine, and usually a parallel file system.

NetCDF-4 exposes the parallel access functionality of HDF5. For more
information about what is required to install and use the parallel
access functions, see the HDF5 web site.

When a netCDF-4 file is opened for parallel access, collective
operations are the default. To use independent access on a variable,
@xref{NF_VAR_PAR_ACCESS}.

@heading Usage 

@example
INTEGER FUNCTION NF_OPEN_PAR(CHARACTER*(*) PATH, INTEGER OMODE, 
                             INTEGER MPI_COMM, INTEGER MPI_INFO, 
                             INTEGER ncid)
@end example

@table @code

@item PATH
File name for netCDF dataset to be opened.
 
@item OMODE
A zero value (or NF_NOWRITE) specifies: open the
dataset with read-only access.

Otherwise, the mode may be NF_WRITE. Setting the NF_WRITE flag opens
the dataset with read-write access. ("Writing" means any kind of
change to the dataset, including appending or changing data, adding or
renaming dimensions, variables, and attributes, or deleting
attributes.)

Setting NF_NETCDF4 is not necessary (or allowed). The file type is
detected automatically.

@item MPI_COMM
The MPI communicator.

@item MPI_INFO
The MPI info.

@item ncid
Returned netCDF ID.

@end table

@heading Errors 

NF_OPEN returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
The specified netCDF dataset does not exist. 

@item
A meaningless mode was specified. 

@item
Not a netCDF-4 file.

@end itemize

@heading Example 
This example is from the test program nf_test/ftst_parallel.F.

@example
!     Reopen the file.
      retval = nf_open_par(FILE_NAME, nf_nowrite, MPI_COMM_WORLD, 
     $     MPI_INFO_NULL, ncid)
      if (retval .ne. nf_noerr) stop 2
@end example

@node NF_REDEF, NF_ENDDEF, NF_OPEN_PAR, Datasets
@section NF_REDEF 
@findex NF_REDEF 

The function NF_REDEF puts an open netCDF dataset into define mode, so
dimensions, variables, and attributes can be added or renamed and
attributes can be deleted.

@heading Usage 

@example
INTEGER FUNCTION NF_REDEF(INTEGER NCID)
@end example

@table @code
@item NCID
netCDF ID, from a previous call to NF_OPEN or NF_CREATE.
@end table

@heading Errors 
NF_REDEF returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
The specified netCDF dataset is already in define mode. 

@item
The specified netCDF dataset was opened for read-only. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 
Here is an example using NF_REDEF to open an existing netCDF dataset
named foo.nc and put it into define mode:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER NCID, STATUS
   ... 
STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)   ! open dataset
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_REDEF(NCID)                      ! put in define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_ENDDEF, NF__ENDDEF, NF_REDEF, Datasets
@section NF_ENDDEF 
@findex NF_ENDDEF 

The function NF_ENDDEF takes an open netCDF dataset out of define
mode. The changes made to the netCDF dataset while it was in define
mode are checked and committed to disk if no problems
occurred. Non-record variables may be initialized to a "fill value" as
well (@pxref{NF_SET_FILL}). The netCDF dataset is then placed in data
mode, so variable data can be read or written.

This call may involve copying data under some
circumstances. @xref{File Structure and Performance,,, netcdf, NetCDF
Users' Guide}.

@heading Usage 

@example
INTEGER FUNCTION NF_ENDDEF(INTEGER NCID)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
@end table

@heading Errors 

NF_ENDDEF returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
The specified netCDF dataset is not in define mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset.
The size of one or more variables exceed the size constraints for
whichever variant of the file format is in use).
@xref{Large File Support,,, netcdf, @value{n-man}}.
@item

@end itemize

@heading Example 

Here is an example using NF_ENDDEF to finish the definitions of a new
netCDF dataset named foo.nc and put it into data mode:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER NCID, STATUS
   ... 
STATUS = NF_CREATE('foo.nc', NF_NOCLOBBER, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)

   ...   ! create dimensions, variables, attributes

STATUS = NF_ENDDEF(NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF__ENDDEF, NF_CLOSE, NF_ENDDEF, Datasets
@section NF__ENDDEF 
@findex NF__ENDDEF 

The function NF__ENDDEF takes an open netCDF dataset out of define
mode. The changes made to the netCDF dataset while it was in define
mode are checked and committed to disk if no problems
occurred. Non-record variables may be initialized to a "fill value" as
well (@pxref{NF_SET_FILL}). The netCDF dataset is then placed in data
mode, so variable data can be read or written.

This call may involve copying data under some
circumstances. @xref{File Structure and Performance,,, netcdf, NetCDF
Users' Guide}.

This function assumes specific characteristics of the netcdf version
1 and version 2 file formats. Users should use nf_enddef in most
circumstances.  Although this function will be available in future netCDF
implementations, it may not continue to have any effect on performance.

The current netcdf file format has three sections, the "header"
section, the data section for fixed size variables, and the data
section for variables which have an unlimited dimension (record
variables).

The header begins at the beginning of the file. The index (offset) of
the beginning of the other two sections is contained in the
header. Typically, there is no space between the sections. This causes
copying overhead to accrue if one wishes to change the size of the
sections, as may happen when changing names of things, text attribute
values, adding attributes or adding variables. Also, for buffered i/o,
there may be advantages to aligning sections in certain ways.

The minfree parameters allow one to control costs of future calls to
nf_redef, nf_enddef by requesting that minfree bytes be available at
the end of the section.

The align parameters allow one to set the alignment of the beginning
of the corresponding sections. The beginning of the section is rounded
up to an index which is a multiple of the align parameter. The flag
value ALIGN_CHUNK tells the library to use the bufrsize (see above)
as the align parameter.

The file format requires mod 4 alignment, so the align parameters
are silently rounded up to multiples of 4. The usual call,

@example
nf_enddef(ncid);
@end example

is equivalent to

@example
nf_enddef(ncid, 0, 4, 0, 4);
@end example

The file format does not contain a "record size" value, this is
calculated from the sizes of the record variables. This unfortunate
fact prevents us from providing minfree and alignment control of the
"records" in a netcdf file. If you add a variable which has an
unlimited dimension, the third section will always be copied with the
new variable added.

@heading Usage 

@example
INTEGER FUNCTION NF_ENDDEF(INTEGER NCID, INTEGER H_MINFREE, INTEGER V_ALIGN,
               INTEGER V_MINFREE, INTEGER R_ALIGN)
@end example

@table @code

@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.

@item H_MINFREE
Sets the pad at the end of the "header" section.

@item V_ALIGN
Controls the alignment of the beginning of the data section for fixed
size variables.

@item V_MINFREE
Sets the pad at the end of the data section for fixed size variables.

@item R_ALIGN
Controls the alignment of the beginning of the data section for
variables which have an unlimited dimension (record variables).

@end table

@heading Errors 

NF__ENDDEF returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
The specified netCDF dataset is not in define mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset.

@item
The size of one or more variables exceed the size constraints for
whichever variant of the file format is in use).
@xref{Large File Support,,, netcdf, @value{n-man}}.
@end itemize

@heading Example 

Here is an example using NF__ENDDEF to finish the definitions of a new
netCDF dataset named foo.nc and put it into data mode:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER NCID, STATUS, H_MINFREE, V_ALIGN, V_MINFREE, R_ALIGN
   ... 
STATUS = NF_CREATE('foo.nc', NF_NOCLOBBER, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)

   ...   ! create dimensions, variables, attributes

H_MINFREE = 512
V_ALIGN = 512
V_MINFREE = 512
R_ALIGN = 512
STATUS = NF_ENDDEF(NCID, H_MINFREE, V_ALIGN, V_MINFREE, R_ALIGN)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_CLOSE, NF_INQ Family, NF__ENDDEF, Datasets
@section NF_CLOSE 
@findex NF_CLOSE 

The function NF_CLOSE closes an open netCDF dataset. If the dataset is
in define mode, NF_ENDDEF will be called before closing. (In this
case, if NF_ENDDEF returns an error, NF_ABORT will automatically be
called to restore the dataset to the consistent state before define
mode was last entered.) After an open netCDF dataset is closed, its
netCDF ID may be reassigned to the next netCDF dataset that is opened
or created.

@heading Usage 
@example
INTEGER FUNCTION NF_CLOSE(INTEGER NCID)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
@end table

@heading Errors 

NF_CLOSE returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
Define mode was entered and the automatic call made to NF_ENDDEF
failed.

@item
The specified netCDF ID does not refer to an open netCDF dataset.
@end itemize

@heading Example 

Here is an example using NF_CLOSE to finish the definitions of a new
netCDF dataset named foo.nc and release its netCDF ID:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER NCID, STATUS
   ... 
STATUS = NF_CREATE('foo.nc', NF_NOCLOBBER, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)

   ...   ! create dimensions, variables, attributes

STATUS = NF_CLOSE(NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_INQ Family, NF_SYNC, NF_CLOSE, Datasets
@section NF_INQ Family
@findex NF_INQ Family
@findex NF_INQ_NDIMS
@findex NF_INQ_NVARS
@findex NF_INQ_NATTS
@findex NF_INQ_UNLIMDIM
@findex NF_INQ_FORMAT

Members of the NF_INQ family of functions return information about an
open netCDF dataset, given its netCDF ID. Dataset inquire functions
may be called from either define mode or data mode. The first
function, NF_INQ, returns values for the number of dimensions, the
number of variables, the number of global attributes, and the
dimension ID of the dimension defined with unlimited length, if
any. The other functions in the family each return just one of these
items of information.

For FORTRAN, these functions include NF_INQ, NF_INQ_NDIMS,
NF_INQ_NVARS, NF_INQ_NATTS, and NF_INQ_UNLIMDIM.  An additional function,
NF_INQ_FORMAT, returns the (rarely needed) format version.

No I/O is performed when these functions are called, since the
required information is available in memory for each open netCDF
dataset.

@heading Usage 
@example
INTEGER FUNCTION NF_INQ          (INTEGER NCID, INTEGER ndims,
                                  INTEGER nvars,INTEGER ngatts,
                                  INTEGER unlimdimid)
INTEGER FUNCTION NF_INQ_NDIMS    (INTEGER NCID, INTEGER ndims)
INTEGER FUNCTION NF_INQ_NVARS    (INTEGER NCID, INTEGER nvars)
INTEGER FUNCTION NF_INQ_NATTS    (INTEGER NCID, INTEGER ngatts)
INTEGER FUNCTION NF_INQ_UNLIMDIM (INTEGER NCID, INTEGER unlimdimid)
INTEGER FUNCTION NF_INQ_FORMAT   (INTEGER NCID, INTEGER format)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item ndims
Returned number of dimensions defined for this netCDF dataset.
 
@item nvars
Returned number of variables defined for this netCDF dataset.
 
@item ngatts
Returned number of global attributes defined for this netCDF dataset.
 
@item unlimdimid
Returned ID of the unlimited dimension, if there is one for this
netCDF dataset. If no unlimited length dimension has been defined, -1
is returned.

@item format
Returned format version, one of 
NF_FORMAT_CLASSIC, NF_FORMAT_64BIT, NF_FORMAT_NETCDF4,
NF_FORMAT_NETCDF4_CLASSIC.
@end table

@heading Errors 

All members of the NF_INQ family return the value NF_NOERR if no
errors occurred. Otherwise, the returned status indicates an
error. Possible causes of errors include:
@itemize

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_INQ to find out about a netCDF dataset
named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID, NDIMS, NVARS, NGATTS, UNLIMDIMID
   ... 
STATUS = NF_OPEN('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ(NCID, NDIMS, NVARS, NGATTS, UNLIMDIMID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_SYNC, NF_ABORT, NF_INQ Family, Datasets
@section NF_SYNC 
@findex NF_SYNC 

The function NF_SYNC offers a way to synchronize the disk copy of a
netCDF dataset with in-memory buffers. There are two reasons you might
want to synchronize after writes:
@itemize

@item
To minimize data loss in case of abnormal termination, or 

@item
To make data available to other processes for reading immediately
after it is written. But note that a process that already had the
dataset open for reading would not see the number of records increase
when the writing process calls NF_SYNC; to accomplish this, the
reading process must call NF_SYNC.
@end itemize

This function is backward-compatible with previous versions of the
netCDF library. The intent was to allow sharing of a netCDF dataset
among multiple readers and one writer, by having the writer call
NF_SYNC after writing and the readers call NF_SYNC before each
read. For a writer, this flushes buffers to disk. For a reader, it
makes sure that the next read will be from disk rather than from
previously cached buffers, so that the reader will see changes made by
the writing process (e.g., the number of records written) without
having to close and reopen the dataset. If you are only accessing a
small amount of data, it can be expensive in computer resources to
always synchronize to disk after every write, since you are giving up
the benefits of buffering.

An easier way to accomplish sharing (and what is now recommended) is
to have the writer and readers open the dataset with the NF_SHARE
flag, and then it will not be necessary to call NF_SYNC at
all. However, the NF_SYNC function still provides finer granularity
than the NF_SHARE flag, if only a few netCDF accesses need to be
synchronized among processes.

It is important to note that changes to the ancillary data, such as
attribute values, are not propagated automatically by use of the
NF_SHARE flag. Use of the NF_SYNC function is still required for this
purpose.

Sharing datasets when the writer enters define mode to change the data
schema requires extra care. In previous releases, after the writer
left define mode, the readers were left looking at an old copy of the
dataset, since the changes were made to a new copy. The only way
readers could see the changes was by closing and reopening the
dataset. Now the changes are made in place, but readers have no
knowledge that their internal tables are now inconsistent with the new
dataset schema. If netCDF datasets are shared across redefinition,
some mechanism external to the netCDF library must be provided that
prevents access by readers during redefinition and causes the readers
to call NF_SYNC before any subsequent access.

When calling NF_SYNC, the netCDF dataset must be in data mode. A
netCDF dataset in define mode is synchronized to disk only when
NF_ENDDEF is called. A process that is reading a netCDF dataset that
another process is writing may call NF_SYNC to get updated with the
changes made to the data by the writing process (e.g., the number of
records written), without having to close and reopen the dataset.

Data is automatically synchronized to disk when a netCDF dataset is
closed, or whenever you leave define mode.

@heading Usage 
@example
INTEGER FUNCTION NF_SYNC(INTEGER NCID)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
@end table

@heading Errors 

NF_SYNC returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
The netCDF dataset is in define mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_SYNC to synchronize the disk writes of a
netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID
   ... 
STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! write data or change attributes
   ... 
STATUS = NF_SYNC(NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_ABORT, NF_SET_FILL, NF_SYNC, Datasets
@section NF_ABORT 
@findex NF_ABORT 

You no longer need to call this function, since it is called
automatically by NF_CLOSE in case the dataset is in define mode and
something goes wrong with committing the changes. The function
NF_ABORT just closes the netCDF dataset, if not in define mode. If the
dataset is being created and is still in define mode, the dataset is
deleted. If define mode was entered by a call to NF_REDEF, the netCDF
dataset is restored to its state before definition mode was entered
and the dataset is closed.

@heading Usage 
@example
INTEGER FUNCTION NF_ABORT(INTEGER NCID)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
@end table

@heading Errors 

NF_ABORT returns the value NF_NOERR if no errors occurred. Otherwise,
the returned status indicates an error. Possible causes of errors
include:
@itemize

@item
When called from define mode while creating a netCDF dataset, deletion
of the dataset failed.

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_ABORT to back out of redefinitions of a
dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID, LATID
   ... 
STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_REDEF(NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_DEF_DIM(NCID, 'LAT', 18, LATID)
IF (STATUS .NE. NF_NOERR) THEN  ! dimension definition failed
   CALL HANDLE_ERR(STATUS)
   STATUS = NF_ABORT(NCID)  ! abort redefinitions
   IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
ENDIF
...
@end example

@node NF_SET_FILL, NF_SET_DEFAULT_FORMAT, NF_ABORT, Datasets
@section NF_SET_FILL 
@findex NF_SET_FILL 

This function is intended for advanced usage, to optimize writes under
some circumstances described below. The function NF_SET_FILL sets the
fill mode for a netCDF dataset open for writing and returns the
current fill mode in a return parameter. The fill mode can be
specified as either NF_FILL or NF_NOFILL. The default behavior
corresponding to NF_FILL is that data is pre-filled with fill values,
that is fill values are written when you create non-record variables
or when you write a value beyond data that has not yet been
written. This makes it possible to detect attempts to read data before
it was written. @xref{Fill Values}, for more information on the use of
fill values. @xref{Attribute Conventions,,,netcdf, @value{n-man}}, for
information about how to define your own fill values.

The behavior corresponding to NF_NOFILL overrides the default behavior
of prefilling data with fill values. This can be used to enhance
performance, because it avoids the duplicate writes that occur when
the netCDF library writes fill values that are later overwritten with
data.

A value indicating which mode the netCDF dataset was already in is
returned. You can use this value to temporarily change the fill mode
of an open netCDF dataset and then restore it to the previous mode.

After you turn on NF_NOFILL mode for an open netCDF dataset, you must
be certain to write valid data in all the positions that will later be
read. Note that nofill mode is only a transient property of a netCDF
dataset open for writing: if you close and reopen the dataset, it will
revert to the default behavior. You can also revert to the default
behavior by calling NF_SET_FILL again to explicitly set the fill mode
to NF_FILL.

There are three situations where it is advantageous to set nofill
mode:
@enumerate
@item
Creating and initializing a netCDF dataset. In this case, you should
set nofill mode before calling NF_ENDDEF and then write completely all
non-record variables and the initial records of all the record
variables you want to initialize.
@item
Extending an existing record-oriented netCDF dataset. Set nofill mode
after opening the dataset for writing, then append the additional
records to the dataset completely, leaving no intervening unwritten
records.
@item
Adding new variables that you are going to initialize to an existing
netCDF dataset. Set nofill mode before calling NF_ENDDEF then write
all the new variables completely.
@end enumerate

If the netCDF dataset has an unlimited dimension and the last record
was written while in nofill mode, then the dataset may be shorter than
if nofill mode was not set, but this will be completely transparent if
you access the data only through the netCDF interfaces.

The use of this feature may not be available (or even needed) in
future releases. Programmers are cautioned against heavy reliance upon
this feature.

@heading Usage 
@example
INTEGER FUNCTION NF_SET_FILL(INTEGER NCID, INTEGER FILLMODE,
                             INTEGER old_mode)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item FILLMODE
Desired fill mode for the dataset, either NF_NOFILL or NF_FILL.
 
@item old_mode
Returned current fill mode of the dataset before this call, either
NF_NOFILL or NF_FILL.
@end table

@heading Errors 

NF_SET_FILL returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:
@itemize

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@item
The specified netCDF ID refers to a dataset open for read-only access. 

@item
The fill mode argument is neither NF_NOFILL nor NF_FILL.. 
@end itemize

@heading Example 

Here is an example using NF_SET_FILL to set nofill mode for subsequent
writes of a netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER NCID, STATUS, OMODE
   ... 
STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! write data with default prefilling behavior
   ... 
STATUS = NF_SET_FILL(NCID, NF_NOFILL, OMODE)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! write data with no prefilling
   ... 
@end example

@node NF_SET_DEFAULT_FORMAT, NF_SET_CHUNK_CACHE, NF_SET_FILL, Datasets
@section NF_SET_DEFAULT_FORMAT 
@findex NF_SET_DEFAULT_FORMAT 

This function is intended for advanced users. 

In version 3.6, netCDF introduced a new data format, the first change
in the underlying binary data format since the netCDF interface was
released. The new format, 64-bit offset format, was introduced to
greatly relax the limitations on creating very large files.

In version 4.0, another new binary format was introduced:
netCDF-4/HDF5.

Users are warned that creating files in the 64-bit offset format makes
them unreadable by the netCDF library prior to version 3.6.0, and
creating files in netcdf-4/HDF5 format makes them unreadable by the
netCDF library prior to version 4.0. For reasons of compatibility,
users should continue to create files in netCDF classic format.

Users who do want to use 64-bit offset or netCDF-4/HDF5 format files
can create them directory from NF_CREATE, using the proper cmode flag.
(@pxref{NF_CREATE}).

The function NF_SET_DEFAULT_FORMAT allows the user to change the
format of the netCDF file to be created by future calls to NF_CREATE
without changing the cmode flag.

This allows the user to convert a program to use the new formats
without changing all calls the NF_CREATE.

Once the default format is set, all future created files will be in
the desired format.

Constants are provided in the netcdf.inc file to be used with this
function: nf_format_classic, nf_format_64bit, nf_format_netcdf4 and
nf_format_netcdf4_classic.

@heading Usage 
@example
INTEGER FUNCTION NF_SET_DEFAULT_FORMAT(INTEGER FORMAT, INTEGER OLD_FORMT)
@end example

@table @code
 
@item FORMAT
Either nf_format_classic, nf_format_64bit, nf_format_netcdf4 or
nf_format_netcdf4_classic.
 
@item OLD_FORMAT
The default format at the time the function is called is returned
here.

@end table

@heading Errors

The following error codes may be returned by this function:

@itemize

@item
An NF_EINVAL error is returned if an invalid default format is
specified.

@end itemize

@heading Example 

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, OLD_FORMAT
   ... 
STATUS = NF_SET_DEFAULT_FORMAT(nf_format_64bit, OLD_FORMAT)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
@end example

@node NF_SET_CHUNK_CACHE, NF_GET_CHUNK_CACHE, NF_SET_DEFAULT_FORMAT, Datasets
@section Set HDF5 Chunk Cache for Future File Opens/Creates: NF_SET_CHUNK_CACHE
@findex nc_set_chunk_cache
@cindex HDF5 chunk cache

This function changes the chunk cache settings in the HDF5
library. The settings apply for subsequent file opens/creates. This
function does not change the chunk cache settings of already open
files.

This affects the per-file chunk cache which the HDF5 layer
maintains. The chunk cache size can be tuned for better performance.

For more information, see the documentation for the H5Pset_cache()
function in the HDF5 library at the HDF5 website:
@uref{@value{hdf5-url}}.

@heading Usage 

@example
INTEGER NF_SET_CHUNK_CACHE(INTEGER SIZE, INTEGER NELEMS, INTEGER PREEMPTION);
@end example

@table @code

@item SIZE
The total size of the raw data chunk cache in MegaBytes.

@item NELEMS
The number slots in the per-variable chunk cache (should be a prime number
larger than the number of chunks in the cache).

@item PREEMPTION
The preemtion value must be between 0 and 100 inclusive and indicates
how much chunks that have been fully read are favored for
preemption. A value of zero means fully read chunks are treated no
differently than other chunks (the preemption is strictly LRU) while a
value of 100 means fully read chunks are always preempted before other
chunks. 

@end table

@heading Return Codes

@table @code

@item NF_NOERR
No error.

@item NF_EINVAL
Parameters size and nelems must be non-zero positive integers, and
preemption must be between zero and 100 (inclusive). An NF_EINVAL will
be returned otherwise.

@end table

@node NF_GET_CHUNK_CACHE,  , NF_SET_CHUNK_CACHE, Datasets
@section Get the HDF5 Chunk Cache Settings for Future File Opens/Creates: NF_GET_CHUNK_CACHE
@findex nc_get_chunk_cache
@cindex HDF5 chunk cache

This function gets the chunk cache settings for the HDF5
library. The settings apply for subsequent file opens/creates. 

This affects the per-file chunk cache which the HDF5 layer
maintains. The chunk cache size can be tuned for better performance.

For more information, see the documentation for the H5Pget_cache()
function in the HDF5 library at the HDF5 website:
@uref{@value{hdf5-url}}.

@heading Usage 

@example
INTEGER NC_GET_CHUNK_CACHE(INTEGER SIZE, INTEGER NELEMS, INTEGER PREEMPTION);
@end example

@table @code

@item SIZE
The total size of the raw data chunk cache will be put here. 

@item NELEMS
The number of chunk slots in the raw data chunk cache hash table will
be put here.  


@item PREEMPTION
The preemption will be put here.  The preemtion value is between 0 and
100 inclusive and indicates how much chunks that have been fully read
are favored for preemption.  A value of zero means fully read chunks
are treated no differently than other chunks (the preemption is
strictly LRU) while a value of 100 means fully read chunks are always
preempted before other chunks. 

@end table

@heading Return Codes

@table @code

@item NC_NOERR
No error.

@end table

@node Groups, Dimensions, Datasets, Top
@chapter Groups
@cindex groups, overview

NetCDF-4 added support for hierarchical groups within netCDF
datasets. 

Groups are identified with a ncid, which identifies both the open
file, and the group within that file. When a file is opened with
NF_OPEN or NF_CREATE, the ncid for the root group of that file is
provided. Using that as a starting point, users can add new groups, or
list and navigate existing groups.

All netCDF calls take a ncid which determines where the call will
take its action. For example, the NF_DEF_VAR function takes a ncid as
its first parameter. It will create a variable in whichever group
its ncid refers to. Use the root ncid provided by NF_CREATE or
NF_OPEN to create a variable in the root group. Or use NF_DEF_GRP to
create a group and use its ncid to define a variable in the new
group.

Variable are only visible in the group in which they are defined. The
same applies to attributes. ``Global'' attributes are defined in
whichever group is refered to by the ncid. 

Dimensions are visible in their groups, and all child groups.

Group operations are only permitted on netCDF-4 files - that is, files
created with the HDF5 flag in nf_create. (@pxref{NF_CREATE}). Groups
are not compatible with the netCDF classic data model, so files
created with the NF_CLASSIC_MODEL file cannot contain groups (except
the root group).

@menu
* NF_INQ_NCID::                 
* NF_INQ_GRPS::                 
* NF_INQ_VARIDS::               
* NF_INQ_DIMIDS::               
* NF_INQ_GRPNAME_LEN::          
* NF_INQ_GRPNAME::              
* NF_INQ_GRPNAME_FULL::         
* NF_INQ_GRP_PARENT::           
* NF_INQ_GRP_NCID::             
* NF_INQ_GRP_FULL_NCID::        
* NF_DEF_GRP::                  
@end menu

@node NF_INQ_NCID, NF_INQ_GRPS, Groups, Groups
@section Find a Group ID: NF_INQ_NCID
@findex NF_INQ_NCID

Given an ncid and group name (NULL or "" gets root group), return
ncid of the named group.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_NCID(INTEGER NCID, CHARACTER*(*) NAME, INTEGER GRPID)
@end example

@table @code

@item NCID
The group id for this operation.

@item NAME
A character array that holds the name of the desired group. Must be
less then NF_MAX_NAME.

@item GRPID
The ID of the group will go here.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_groups.F.

@example
C     Check getting the group by name
      retval = nf_inq_ncid(ncid, group_name, grpid_in)
      if (retval .ne. nf_noerr) call handle_err(retval)

@end example

@node NF_INQ_GRPS, NF_INQ_VARIDS, NF_INQ_NCID, Groups
@section Get a List of Groups in a Group: NF_INQ_GRPS
@findex NF_INQ_GRPS

Given a location id, return the number of groups it contains, and an
array of their ncids.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_GRPS(INTEGER NCID, INTEGER NUMGRPS, INTEGER NCIDS)
@end example

@table @code

@item NCID
The group id for this operation.

@item NUMGRPS
An integer which will get number of groups in this group. 

@item NCIDS
An array of ints which will receive the IDs of all the groups in this
group.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_groups.F.

@example
C     What groups are there from the root group?
      retval = nf_inq_grps(ncid, ngroups_in, grpids)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_VARIDS, NF_INQ_DIMIDS, NF_INQ_GRPS, Groups
@section Find all the Variables in a Group: NF_INQ_VARIDS
@findex NF_INQ_VARIDS

Find all varids for a location.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_VARIDS(INTEGER NCID, INTEGERS VARIDS)
@end example

@table @code

@item NCID
The group id for this operation.

@item VARIDS
An already allocated array to store the list of varids. Use
nf_inq_nvars to find out how many variables there are. (@pxref{NF_INQ
Family}).

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_groups.F.

@example
C     Check varids in subgroup.
      retval = nf_inq_varids(subgrp_in, nvars, varids_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_DIMIDS, NF_INQ_GRPNAME_LEN, NF_INQ_VARIDS, Groups
@section Find all Dimensions Visible in a Group: NF_INQ_DIMIDS
@findex NF_INQ_DIMIDS

Find all dimids for a location. This finds all dimensions in a group,
or any of its parents.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_DIMIDS(INTEGER NCID, INTEGER NDIMS, INTEGER DIMIDS, INTEGER INCLUDE_PARENTS)
@end example

@table @code

@item NCID
The group id for this operation.

@item NDIMS
Returned number of dimensions for this location.  If INCLUDE_PARENTS
is non-zero, number of dimensions visible from this group, which
includes dimensions in parent groups.

@item DIMIDS
An array of ints when the dimids of the visible dimensions will be
stashed. Use nf_inq_ndims to find out how many dims are visible from
this group. (@pxref{NF_INQ Family}).

@item INCLUDE_PARENTS
If zero, only the group specified by NCID will be searched for
dimensions. Otherwise parent groups will be searched too.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_groups.F.

@example
C     Check dimids in subgroup.
      retval = nf_inq_dimids(subgrp_in, ndims, dimids_in, 0)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (ndims .ne. 2 .or. dimids_in(1) .ne. dimids(1) .or.
     &     dimids_in(2) .ne. dimids(2)) stop 2

@end example

@node NF_INQ_GRPNAME_LEN, NF_INQ_GRPNAME, NF_INQ_DIMIDS, Groups
@section Find the Length of a Group's Name: NF_INQ_GRPNAME_LEN
@findex NF_INQ_GRPNAME_LEN

Given ncid, find length of the full name. (Root group is named "/",
with length 1.)

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_GRPNAME_LEN(INTEGER NCID, INTEGER LEN)
@end example

@table @code

@item NCID
The group id for this operation.

@item LEN
An integer where the length will be placed.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_groups.F.

@example
C     Check the length of the full name.
      retval = nf_inq_grpname_len(grpids(1), full_name_len)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_GRPNAME, NF_INQ_GRPNAME_FULL, NF_INQ_GRPNAME_LEN, Groups
@section Find a Group's Name: NF_INQ_GRPNAME
@findex NF_INQ_GRPNAME

Given ncid, find relative name of group. (Root group is named "/").

The name provided by this function is relative to the parent
group. For a full path name for the group is, with all parent groups
included, separated with a forward slash (as in Unix directory names) @xref{NF_INQ_GRPNAME_FULL}.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_GRPNAME(INTEGER NCID, CHARACTER*(*) NAME)
@end example

@table @code

@item NCID
The group id for this operation.

@item NAME
The name of the
group will be copied to this character array. The name will be less
than NF_MAX_NAME in length.
@item

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_groups.F.

@example
C     Check the name of the root group.
      retval = nf_inq_grpname(ncid, name_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (name_in(1:1) .ne. '/') stop 2
@end example

@node NF_INQ_GRPNAME_FULL, NF_INQ_GRP_PARENT, NF_INQ_GRPNAME, Groups
@section Find a Group's Full Name: NF_INQ_GRPNAME_FULL
@findex NF_INQ_GRPNAME_FULL

Given ncid, find complete name of group. (Root group is named "/").

The name provided by this function is a full path name for the group
is, with all parent groups included, separated with a forward slash
(as in Unix directory names). For a name relative to the parent group
@xref{NF_INQ_GRPNAME}.

To find the length of the full name @xref{NF_INQ_GRPNAME_LEN}.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_GRPNAME_FULL(INTEGER NCID, INTEGER LEN, CHARACTER*(*) NAME)
@end example

@table @code

@item NCID
The group id for this operation.

@item LEN
The length of the full group name will go here.      

@item NAME
The name of the group will be copied to this character array. 

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_groups.F.

@example
C     Check the full name.
      retval = nf_inq_grpname_full(grpids(1), full_name_len, name_in2)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_GRP_PARENT, NF_INQ_GRP_NCID, NF_INQ_GRPNAME_FULL, Groups
@section Find a Group's Parent: NF_INQ_GRP_PARENT
@findex NF_INQ_GRP_PARENT

Given ncid, find the ncid of the parent group. 

When used with the root group, this function returns the NF_ENOGRP
error (since the root group has no parent.)

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_GRP_PARENT(INTEGER NCID, INTEGER PARENT_NCID)
@end example

@table @code

@item NCID
The group id.

@item PARENT_NCID
The ncid of the parent group will be copied here.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENOGRP
No parent group found (i.e. this is the root group).

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_groups.F.

@example
C     Check the parent ncid.
      retval = nf_inq_grp_parent(grpids(1), grpid_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_GRP_NCID, NF_INQ_GRP_FULL_NCID, NF_INQ_GRP_PARENT, Groups
@section Find a Group by Name: NF_INQ_GRP_NCID
@findex NF_INQ_GRP_PARENT

Given a group name an an ncid, find the ncid of the group id. 

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_GRP_NCID(INTEGER NCID, CHARACTER GRP_NAME, INTEGER GRP_NCID)
@end example

@table @code

@item NCID
The group id to look in.

@item GRP_NAME
The name of the group that should be found.

@item GRP_NCID
This will get the group id, if it is found.

@end table

@heading Return Codes

The following return codes may be returned by this function.

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_EINVAL
No name provided or name longer than NF_MAX_NAME.

@item NF_ENOGRP
Named group not found.

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example
This example is from nf_test/ftst_types3.F.

@example
C     Go to a child group and find the id of our type.
      retval = nf_inq_grp_ncid(ncid, group_name, sub_grpid)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_GRP_FULL_NCID, NF_DEF_GRP, NF_INQ_GRP_NCID, Groups
@section Find a Group by its Fully-qualified Name: NF_INQ_GRP_FULL_NCID
@findex NF_INQ_GRP_PARENT

Given a fully qualified group name an an ncid, find the ncid of the
group id.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_GRP_FULL_NCID(INTEGER NCID, CHARACTER FULL_NAME, INTEGER GRP_NCID)
@end example

@table @code

@item NCID
The group id to look in.

@item FULL_NAME
The fully-qualified group name.

@item GRP_NCID
This will get the group id, if it is found.

@end table

@heading Return Codes

The following return codes may be returned by this function.

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_EINVAL
No name provided or name longer than NF_MAX_NAME.

@item NF_ENOGRP
Named group not found.

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example
This example is from nf_test/ftst_groups.F.

@example
C     Check the full name of the root group (also "/").
      retval = nf_inq_grpname_full(ncid, full_name_len, name_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_DEF_GRP,  , NF_INQ_GRP_FULL_NCID, Groups
@section Create a New Group: NF_DEF_GRP
@findex NF_DEF_GRP

Create a group. Its location id is returned in new_ncid. 

@heading Usage 

@example
INTEGER FUNCTION NF_DEF_GRP(INTEGER PARENT_NCID, CHARACTER*(*) NAME,
        INTEGER NEW_NCID)
@end example

@table @code

@item PARENT_NCID
The group id of the parent group.

@item NAME
The name of the new group, which must be different from the name of
any variable within the same parent group.

@item NEW_NCID
The ncid of the new group will be placed there.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENAMEINUSE
That name is in use. Group names must be unique within a group.

@item NF_EMAXNAME
Name exceed max length NF_MAX_NAME.

@item NF_EBADNAME
Name contains illegal characters.

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag HDF5. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@item NF_EPERM
Attempt to write to a read-only file.

@item NF_ENOTINDEFINE
Not in define mode.

@end table

@heading Example

In this exampe rom nf_test/ftst_groups.F, a groups is reated, and then
a sub-group is created in that group.

@example
C     Create the netCDF file.
      retval = nf_create(file_name, NF_NETCDF4, ncid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Create a group and a subgroup.
      retval = nf_def_grp(ncid, group_name, grpid)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_def_grp(grpid, sub_group_name, sub_grpid)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node Dimensions, User Defined Data Types, Groups, Top
@chapter Dimensions

@menu
* Dimensions Introduction::     
* NF_DEF_DIM::                  
* NF_INQ_DIMID::                
* NF_INQ_DIM Family::           Inquire about a Dimension
* NF_RENAME_DIM::               
@end menu

@node Dimensions Introduction, NF_DEF_DIM, Dimensions, Dimensions
@section Dimensions Introduction

Dimensions for a netCDF dataset are defined when it is created, while
the netCDF dataset is in define mode. Additional dimensions may be
added later by reentering define mode. A netCDF dimension has a name
and a length. At most one dimension in a netCDF dataset can have the
unlimited length, which means variables using this dimension can grow
along this dimension.

There is a suggested limit (100) to the number of dimensions that can
be defined in a single netCDF dataset. The limit is the value of the
predefined macro NF_MAX_DIMS. The purpose of the limit is to make
writing generic applications simpler. They need only provide an array
of NF_MAX_DIMS dimensions to handle any netCDF dataset. The
implementation of the netCDF library does not enforce this advisory
maximum, so it is possible to use more dimensions, if necessary, but
netCDF utilities that assume the advisory maximums may not be able to
handle the resulting netCDF datasets.

Ordinarily, the name and length of a dimension are fixed when the
dimension is first defined. The name may be changed later, but the
length of a dimension (other than the unlimited dimension) cannot be
changed without copying all the data to a new netCDF dataset with a
redefined dimension length.

A netCDF dimension in an open netCDF dataset is referred to by a small
integer called a dimension ID. In the FORTRAN interface, dimension IDs
are 1, 2, 3, ..., in the order in which the dimensions were defined.

Operations supported on dimensions are:
@itemize

@item
Create a dimension, given its name and length. 

@item
Get a dimension ID from its name. 

@item
Get a dimension's name and length from its ID. 

@item
Rename a dimension. 
@end itemize

@node NF_DEF_DIM, NF_INQ_DIMID, Dimensions Introduction, Dimensions
@section NF_DEF_DIM 
@findex NF_DEF_DIM

The function NF_DEF_DIM adds a new dimension to an open netCDF dataset
in define mode. It returns (as an argument) a dimension ID, given the
netCDF ID, the dimension name, and the dimension length. At most one
unlimited length dimension, called the record dimension, may be
defined for each netCDF dataset.

@heading Usage 
@example
INTEGER FUNCTION NF_DEF_DIM (INTEGER NCID, CHARACTER*(*) NAME,
                          INTEGER LEN, INTEGER dimid)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item NAME
Dimension name.
 
@item LEN
Length of dimension; that is, number of values for this dimension as
an index to variables that use it. This should be either a positive
integer or the predefined constant NF_UNLIMITED.
 
@item dimid
Returned dimension ID.
@end table

@heading Errors 

NF_DEF_DIM returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:
@itemize

@item
The netCDF dataset is not in definition mode. 

@item
The specified dimension name is the name of another existing
dimension.

@item
The specified length is not greater than zero. 

@item
The specified length is unlimited, but there is already an unlimited
length dimension defined for this netCDF dataset.

@item
The specified netCDF ID does not refer to an open netCDF dataset.

@end itemize

@heading Example 

Here is an example using NF_DEF_DIM to create a dimension named lat of
length 18 and a unlimited dimension named rec in a new netCDF dataset
named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID, LATID, RECID
   ... 
STATUS = NF_CREATE('foo.nc', NF_NOCLOBBER, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_DEF_DIM(NCID, 'lat', 18, LATID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_DEF_DIM(NCID, 'rec', NF_UNLIMITED, RECID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_INQ_DIMID, NF_INQ_DIM Family, NF_DEF_DIM, Dimensions
@section NF_INQ_DIMID 
@findex NF_INQ_DIMID 

The function NF_INQ_DIMID returns (as an argument) the ID of a netCDF
dimension, given the name of the dimension. If ndims is the number of
dimensions defined for a netCDF dataset, each dimension has an ID
between 1 and ndims.

@heading Usage 
@example
INTEGER FUNCTION NF_INQ_DIMID (INTEGER NCID, CHARACTER*(*) NAME,
                               INTEGER dimid)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item NAME
Dimension name.
 
@item dimid
Returned dimension ID.
@end table
 
@heading Errors 

NF_INQ_DIMID returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The name that was specified is not the name of a dimension in the
netCDF dataset.  

@item
The specified netCDF ID does not refer to an open netCDF dataset.

@end itemize

@heading Example 

Here is an example using NF_INQ_DIMID to determine the dimension ID of
a dimension named lat, assumed to have been defined previously in an
existing netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID, LATID
   ... 
STATUS = NF_OPEN('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_DIMID(NCID, 'lat', LATID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_INQ_DIM Family, NF_RENAME_DIM, NF_INQ_DIMID, Dimensions
@section NF_INQ_DIM Family
@findex NF_INQ_DIM Family

This family of functions returns information about a netCDF
dimension. Information about a dimension includes its name and its
length. The length for the unlimited dimension, if any, is the number
of records written so far.

The functions in this family include NF_INQ_DIM, NF_INQ_DIMNAME, and
NF_INQ_DIMLEN. The function NF_INQ_DIM returns all the information
about a dimension; the other functions each return just one item of
information.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_DIM     (INTEGER NCID, INTEGER DIMID,
                                 CHARACTER*(*) name, INTEGER len)
INTEGER FUNCTION NF_INQ_DIMNAME (INTEGER NCID, INTEGER DIMID,
                                 CHARACTER*(*) name)
INTEGER FUNCTION NF_INQ_DIMLEN  (INTEGER NCID, INTEGER DIMID,
                                 INTEGER len)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE. 
 
@item DIMID
Dimension ID, from a previous call to NF_INQ_DIMID or NF_DEF_DIM.
 
@item NAME
Returned dimension name. The caller must allocate space for the
returned name. The maximum possible length, in characters, of a
dimension name is given by the predefined constant NF_MAX_NAME.
 
@item len
Returned length of dimension. For the unlimited dimension, this is the
current maximum value used for writing any variables with this
dimension, that is the maximum record number.
@end table

@heading Errors 

These functions return the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The dimension ID is invalid for the specified netCDF dataset. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@end itemize

@heading Example 

Here is an example using NF_INQ_DIM to determine the length of a
dimension named lat, and the name and current maximum length of the
unlimited dimension for an existing netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID, LATID, LATLEN, RECID, NRECS
CHARACTER*(NF_MAX_NAME) LATNAM, RECNAM
   ... 
STATUS = NF_OPEN('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
! get ID of unlimited dimension
STATUS = NF_INQ_UNLIMDIM(NCID, RECID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_DIMID(NCID, 'lat', LATID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
! get lat length
STATUS = NF_INQ_DIMLEN(NCID, LATID, LATLEN)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
! get unlimited dimension name and current length
STATUS = NF_INQ_DIM(NCID, RECID, RECNAME, NRECS)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_RENAME_DIM,  , NF_INQ_DIM Family, Dimensions
@section NF_RENAME_DIM 
@findex NF_RENAME_DIM 

The function NF_RENAME_DIM renames an existing dimension in a netCDF
dataset open for writing. If the new name is longer than the old name,
the netCDF dataset must be in define mode. You cannot rename a
dimension to have the same name as another dimension.

@heading Usage 

@example
INTEGER FUNCTION NF_RENAME_DIM (INTEGER NCID, INTEGER DIMID,
                                CHARACTER*(*) NAME)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item DIMID
Dimension ID, from a previous call to NF_INQ_DIMID or NF_DEF_DIM.
 
@item NAME
New dimension name.

@end table

@heading Errors 

NF_RENAME_DIM returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The new name is the name of another dimension. 

@item
The dimension ID is invalid for the specified netCDF dataset. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@item
The new name is longer than the old name and the netCDF dataset is not
in define mode.
@end itemize

@heading Example 
Here is an example using NF_RENAME_DIM to rename the dimension lat to
latitude in an existing netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID, LATID
   ... 
STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! put in define mode to rename dimension
STATUS = NF_REDEF(NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_INQ_DIMID(NCID, 'lat', LATID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_RENAME_DIM(NCID, LATID, 'latitude')
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
! leave define mode
STATUS = NF_ENDDEF(NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node User Defined Data Types, Variables, Dimensions, Top
@chapter User Defined Data Types
@cindex variable length array type, overview
@cindex user defined types

@menu
* User Defined Types::          
* NF_INQ_TYPEIDS::              
* NF_INQ_TYPEID::               
* NF_INQ_TYPE::                 
* NF_INQ_USER_TYPE::            
* Compound Types::              
* Variable Length Array::       
* Opaque Type::                 
* Enum Type::                   
@end menu

@node User Defined Types, NF_INQ_TYPEIDS, User Defined Data Types, User Defined Data Types
@section User Defined Types Introduction
@cindex user defined types, overview

NetCDF-4 has added support for four different user defined data types.

@table @code

@item compound type
Like a C struct, a compound type is a collection of types, including
other user defined types, in one package.

@item variable length array type
The variable length array may be used to store ragged arrays.

@item opaque type
This type has only a size per element, and no other type information.

@item enum type
Like an enumeration in C, this type lets you assign text values to
integer values, and store the integer values.

@end table

Users may construct user defined type with the various NF_DEF_*
functions described in this section. They may learn about user defined
types by using the NF_INQ_ functions defined in this section.

Once types are constructed, define variables of the new type with
NF_DEF_VAR (@pxref{NF_DEF_VAR}). Write to them with NF_PUT_VAR1,
NF_PUT_VAR, NF_PUT_VARA, or NF_PUT_VARS (@pxref{Variables}). Read data
of user-defined type with NF_GET_VAR1, NF_GET_VAR, NF_GET_VARA, or
NF_GET_VARS (@pxref{Variables}).

Create attributes of the new type with NF_PUT_ATT
(@pxref{NF_PUT_ATT_ type}). Read attributes of the new type with NF_GET_ATT
(@pxref{NF_GET_ATT_ type}).

@node NF_INQ_TYPEIDS, NF_INQ_TYPEID, User Defined Types, User Defined Data Types
@section Learn the IDs of All Types in Group: NF_INQ_TYPEIDS
@findex NF_INQ_TYPEIDS

Learn the number of types defined in a group, and their IDs.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_TYPEIDS(INTEGER NCID, INTEGER NTYPES, 
        INTEGER TYPEIDS)
@end example

@table @code

@item NCID
The group id.

@item NTYPES
A pointer to int which will get the number of types defined in the
group. If NULL, ignored.

@item TYPEIDS
A pointer to an int array which will get the typeids. If NULL,
ignored.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@end table

@heading Example

The following example is from the test program nf_test/ftst_vars3.F.

@example
      retval = nf_inq_typeids(ncid, num_types, typeids)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_TYPEID, NF_INQ_TYPE, NF_INQ_TYPEIDS, User Defined Data Types
@section Find a Typeid from Group and Name: NF_INQ_TYPEID
@findex NF_INQ_TYPEID

Given a group ID and a type name, find the ID of the type. If the type
is not found in the group, then the parents are searched. If still not
found, the entire file is searched.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_TYPEID(INTEGER NCID, CHARACTER NAME, NF_TYPE TYPEIDP)
@end example

@table @code

@item NCID
The group id.

@item NAME
The name of a type.

@item TYPEIDP
The typeid of the named type (if found).

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad ncid.

@item NF_EBADTYPE
Can't find type.

@end table

@heading Example

The following example is from nf_test/ftst_types3.F:

@example
C     Go to a child group and find the id of our type.
      retval = nf_inq_grp_ncid(ncid, group_name, sub_grpid)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_inq_typeid(sub_grpid, type_name, typeid_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_TYPE, NF_INQ_USER_TYPE, NF_INQ_TYPEID, User Defined Data Types
@section Learn About a User Defined Type: NF_INQ_TYPE
@findex NF_INQ_TYPE

Given an ncid and a typeid, get the information about a type. This
function will work on any type, including atomic and any user defined
type, whether compound, opaque, enumeration, or variable length array.

For even more information about a user defined type @ref{NF_INQ_USER_TYPE}.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_TYPE(INTEGER NCID, INTEGER XTYPE, 
        CHARACTER*(*) NAME, INTEGER SIZE)
@end example

@table @code

@item NCID
The ncid for the group containing the type (ignored for atomic types).

@item XTYPE
The typeid for this type, as returned by NF_DEF_COMPOUND,
NF_DEF_OPAQUE, NF_DEF_ENUM, NF_DEF_VLEN, or NF_INQ_VAR, or as found in
netcdf.inc in the list of atomic types (NF_CHAR, NF_INT, etc.).

@item NAME
The name of the user defined type will be copied here. It will be
NF_MAX_NAME bytes or less. For atomic types, the type name from CDL
will be given.

@item SIZEP
The (in-memory) size of the type (in bytes) will be copied here. VLEN
type size is the size of one vlen sturture (i.e. the sice of
nc_vlen_t). String size is returned as the size of one C character
pointer.

@end table

@heading Return Codes

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPEID
Bad typeid.

@item NF_ENOTNC4
Seeking a user-defined type in a netCDF-3 file.

@item NF_ESTRICTNC3
Seeking a user-defined type in a netCDF-4 file for which classic model
has been turned on.

@item NF_EBADGRPID
Bad group ID in ncid.

@item NF_EBADID
Type ID not found.

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from the test program nf_test/ftst_vars3.F, and it uses all the
possible inquiry functions on an enum type.

@example
C     Check the enum type.
      retval = NF_INQ_TYPEIDS(ncid, num_types, typeids)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (num_types .ne. MAX_TYPES) stop 2
      retval = nf_inq_enum(ncid, typeids(1), type_name, base_type, 
     &     base_size, num_members)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (base_type .ne. NF_INT .or. num_members .ne. 2) stop 2
      retval = nf_inq_enum_member(ncid, typeids(1), 1, member_name, 
     &     member_value)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (member_name(1:len(one_name)) .ne. one_name) stop 2

@end example

@node NF_INQ_USER_TYPE, Compound Types, NF_INQ_TYPE, User Defined Data Types
@section Learn About a User Defined Type: NF_INQ_USER_TYPE
@findex NF_INQ_USER_TYPE

Given an ncid and a typeid, get the information about a user defined
type. This function will work on any user defined type, whether
compound, opaque, enumeration, or variable length array.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_USER_TYPE(INTEGER NCID, INTEGER XTYPE,
        CHARACTER*(*) NAME, INTEGER SIZE, INTEGER BASE_NF_TYPE, 
        INTEGER NFIELDS, INTEGER CLASS)
@end example

@table @code

@item NCID
The ncid for the group containing the user defined type.

@item XTYPE
The typeid for this type, as returned by NF_DEF_COMPOUND,
NF_DEF_OPAQUE, NF_DEF_ENUM, NF_DEF_VLEN, or NF_INQ_VAR.

@item NAME
The name of the user defined type will be copied here. It
will be NF_MAX_NAME bytes or less.

@item SIZE
The (in-memory) size of the user defined type will be copied here.

@item BASE_NF_TYPE
The base typeid will be copied here for vlen and enum types.

@item NFIELDS
The number of fields will be copied here for enum and compound types.

@item CLASS
The class of the user defined type, NF_VLEN, NF_OPAQUE, NF_ENUM, or
NF_COMPOUND, will be copied here.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPEID
Bad typeid.

@item NF_EBADFIELDID
Bad fieldid.

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_types2.F.

@example
C     Check the type.
      retval = nf_inq_user_type(ncid, typeids(1), name_in, size_in, 
     &     base_type_in, nfields_in, class_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node Compound Types, Variable Length Array, NF_INQ_USER_TYPE, User Defined Data Types
@section Compound Types Introduction
@cindex compound types, overview

NetCDF-4 added support for compound types, which allow users to
construct a new type - a combination of other types, like a C struct.

Compound types are not supported in classic or 64-bit offset format
files. 

To write data in a compound type, first use nf_def_compound to create the
type, multiple calls to nf_insert_compound to add to the compound type, and
then write data with the appropriate nf_put_var1, nf_put_vara,
nf_put_vars, or nf_put_varm call.

To read data written in a compound type, you must know its
structure. Use the NF_INQ_COMPOUND functions to learn about the compound
type.

In Fortran a character buffer must be used for the compound data. The
user must read the data from within that buffer in the same way that
the C compiler which compiled netCDF would store the structure.

The use of compound types introduces challenges and portability issues
for Fortran users.

@menu
* NF_DEF_COMPOUND::             
* NF_INSERT_COMPOUND::          
* NF_INSERT_ARRAY_COMPOUND::    
* NF_INQ_COMPOUND::             
* NF_INQ_COMPOUND_FIELD::       
@end menu

@node NF_DEF_COMPOUND, NF_INSERT_COMPOUND, Compound Types, Compound Types
@subsection Creating a Compound Type: NF_DEF_COMPOUND
@findex NF_DEF_COMPOUND

Create a compound type. Provide an ncid, a name, and a total size (in
bytes) of one element of the completed compound type.

After calling this function, fill out the type with repeated calls to
NF_INSERT_COMPOUND (@pxref{NF_INSERT_COMPOUND}). Call
NF_INSERT_COMPOUND once for each field you wish to insert into the
compound type.

Note that there does not seem to be a way to read such types into
structures in Fortran 90 (and there are no structures in Fortran
77). 

Fortran users may use character buffers to read and write
compound types.

@heading Usage 

@example
INTEGER FUNCTION NF_DEF_COMPOUND(INTEGER NCID, INTEGER SIZE,
        CHARACTER*(*) NAME, INTEGER TYPEIDP)
@end example

@table @code

@item NCID
The groupid where this compound type will be created.

@item SIZE
The size, in bytes, of the compound type. 

@item NAME
The name of the new compound type.

@item TYPEIDP
The typeid of the new type will be placed here.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENAMEINUSE
That name is in use. Compound type names must be unique in the data
file. 

@item NF_EMAXNAME
Name exceeds max length NF_MAX_NAME.

@item NF_EBADNAME
Name contains illegal characters.

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag NF_NETCDF4. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@item NF_EPERM
Attempt to write to a read-only file.

@item NF_ENOTINDEFINE
Not in define mode.

@end table

@heading Example

This example is from nf_test/ftst_types2.F.

@example
C     Define a compound type.
      retval = nf_def_compound(ncid, cmp_size, type_name, 
     &     cmp_typeid)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INSERT_COMPOUND, NF_INSERT_ARRAY_COMPOUND, NF_DEF_COMPOUND, Compound Types
@subsection Inserting a Field into a Compound Type: NF_INSERT_COMPOUND
@findex NF_INSERT_COMPOUND

Insert a named field into a compound type.

@heading Usage 

@example
INTEGER FUNTION NF_INSERT_COMPOUND(INTEGER TYPEID, CHARACTER*(*) NAME, INTEGER OFFSET, 
        INTEGER FIELD_TYPEID)
@end example

@table @code

@item TYPEID
The typeid for this compound type, as returned by NF_DEF_COMPOUND, or
NF_INQ_VAR.

@item NAME
The name of the new field.

@item OFFSET
Offset in byte from the beginning of the compound type for this
field.

@item FIELD_TYPEID
The type of the field to be inserted.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENAMEINUSE
That name is in use. Field names must be unique within a compound type.

@item NF_EMAXNAME
Name exceed max length NF_MAX_NAME.

@item NF_EBADNAME
Name contains illegal characters.

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag NF_NETCDF4. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@item NF_ENOTINDEFINE
Not in define mode.

@end table

@heading Example

This example is from nf_test/ftst_types.F.

@example
C     Define a compound type.
      retval = nf_def_compound(ncid, WIND_T_SIZE, type_name, 
     &     wind_typeid)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_insert_compound(ncid, wind_typeid, u_name, 0, NF_INT)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_insert_compound(ncid, wind_typeid, v_name, 4, NF_INT)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INSERT_ARRAY_COMPOUND, NF_INQ_COMPOUND, NF_INSERT_COMPOUND, Compound Types
@subsection Inserting an Array Field into a Compound Type: NF_INSERT_ARRAY_COMPOUND
@findex NF_INSERT_ARRAY_COMPOUND

Insert a named array field into a compound type.

@heading Usage 

@example
INTEGER FUNCTION NF_INSERT_ARRAY_COMPOUND(INTEGER NCID, INTEGER XTYPE,
        CHARACTER*(*) NAME, INTEGER OFFSET, INTEGER FIELD_TYPEID,
        INTEGER NDIMS, INTEGER DIM_SIZES) 
@end example

@table @code

@item NCID
The ID of the file that contains the array type and the compound type.

@item XTYPE
The typeid for this compound type, as returned by nf_def_compound, or
nf_inq_var.

@item NAME
The name of the new field.

@item OFFSET
Offset in byte from the beginning of the compound type for this
field.

@item FIELD_TYPEID
The base type of the array to be inserted.

@item NDIMS
The number of dimensions for the array to be inserted.

@item DIM_SIZES
An array containing the sizes of each dimension.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENAMEINUSE
That name is in use. Field names must be unique within a compound type.

@item NF_EMAXNAME
Name exceed max length NF_MAX_NAME.

@item NF_EBADNAME
Name contains illegal characters.

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag NF_NETCDF4. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@item NF_ENOTINDEFINE
Not in define mode.

@item NF_ETYPEDEFINED
Attempt to change type that has already been committed. The first time
the file leaves define mode, all defined types are committed, and
can't be changed. If you wish to add an array to a compound type, you
must do so before the compound type is committed.

@end table

@heading Example

This example is from nf_test/ftst_types2.F.

@example
C     Define a compound type.
      retval = nf_def_compound(ncid, cmp_size, type_name, 
     &     cmp_typeid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Include an array.
      dim_sizes(1) = NX
      dim_sizes(2) = NY
      retval = nf_insert_array_compound(ncid, cmp_typeid, ary_name, 0, 
     &     NF_INT, NDIMS, dim_sizes)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_COMPOUND, NF_INQ_COMPOUND_FIELD, NF_INSERT_ARRAY_COMPOUND, Compound Types
@subsection Learn About a Compound Type: NF_INQ_COMPOUND
@findex NF_INQ_COMPOUND
@findex NF_INQ_COMPOUND_NAME
@findex NF_INQ_COMPOUND_SIZE
@findex NF_INQ_COMPOUND_NFIELDS

Get the number of fields, length in bytes, and name of a compound
type.

In addtion to the NF_INQ_COMPOUND function, three additional functions
are provided which get only the name, size, and number of fields.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_COMPOUND(INTEGER NCID, INTEGER XTYPE,
        CHARACTER*(*) NAME, INTEGER SIZEP, INTEGER NFIELDSP)

INTEGER FUNCTION NF_INQ_COMPOUND_NAME(INTEGER NCID, INTEGER XTYPE, 
        CHARACTER*(*) NAME)

INTEGER FUNCTION NF_INQ_COMPOUND_SIZE(INTEGER NCID, INTEGER XTYPE, 
        INTEGER SIZEP)

INTEGER FUNCTION NF_INQ_COMPOUND_NFIELDS(INTEGER NCID, INTEGER XTYPE, 
        INTEGER NFIELDSP)
@end example

@table @code

@item NCID
The ID of any group in the file that contains the compound type.

@item XTYPE
The typeid for this compound type, as returned by NF_DEF_COMPOUND, or
NF_INQ_VAR.

@item NAME
Character array which will get the name of the compound type. It will
have a maximum length of NF_MAX_NAME.

@item SIZEP
The size of the compound type in bytes will be put here.

@item NFIELDSP
The number of fields in the compound type will be placed here.

@end table

@heading Return Codes

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Couldn't find this ncid.

@item NF_ENOTNC4
Not a netCDF-4/HDF5 file.

@item NF_ESTRICTNC3
A netCDF-4/HDF5 file, but with CLASSIC_MODEL. No user defined types
are allowed in the classic model.

@item NF_EBADTYPE
This type not a compound type.

@item NF_EBADTYPEID
Bad type id. 

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_types.F.

@example
C     Check it differently.
      retval = nf_inq_compound(ncid, typeids(1), name_in, size_in, 
     &     nfields_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (name_in(1:len(type_name)) .ne. type_name .or. 
     &     size_in .ne. WIND_T_SIZE .or. nfields_in .ne. 2) stop 2

C     Check it one piece at a time.
      retval = nf_inq_compound_nfields(ncid, typeids(1), nfields_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (nfields_in .ne. 2) stop 2
      retval = nf_inq_compound_size(ncid, typeids(1), size_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (size_in .ne. WIND_T_SIZE) stop 2
      retval = nf_inq_compound_name(ncid, typeids(1), name_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (name_in(1:len(type_name)) .ne. type_name) stop 2
@end example

@node NF_INQ_COMPOUND_FIELD,  , NF_INQ_COMPOUND, Compound Types
@subsection Learn About a Field of a Compound Type: NF_INQ_COMPOUND_FIELD
@findex NF_INQ_COMPOUND_FIELD
@findex NF_INQ_COMPOUND_FIELDNAME
@findex NF_INQ_COMPOUND_FIELDINDEX
@findex NF_INQ_COMPOUND_FIELDOFFSET
@findex NF_INQ_COMPOUND_FIELDTYPE
@findex NF_INQ_COMPOUND_FIELDNDIMS
@findex NF_INQ_COMPOUND_FIELDDIM_SIZES

Get information about one of the fields of a compound type.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_COMPOUND_FIELD(INTEGER NCID, INTEGER XTYPE,
        INTEGER FIELDID, CHARACTER*(*) NAME, INTEGER OFFSETP, 
        INTEGER FIELD_TYPEIDP, INTEGER NDIMSP, INTEGER DIM_SIZESP)

INTEGER FUNCTION NF_INQ_COMPOUND_FIELDNAME(INTEGER TYPEID, 
        INTEGER FIELDID, CHARACTER*(*) NAME)

INTEGER FUNCTION NF_INQ_COMPOUND_FIELDINDEX(INTEGER TYPEID,    
        CHARACTER*(*) NAME, INTEGER FIELDIDP)

INTEGER FUNCTION NF_INQ_COMPOUND_FIELDOFFSET(INTEGER TYPEID, 
        INTEGER FIELDID, INTEGER OFFSETP)

INTEGER FUNCTION NF_INQ_COMPOUND_FIELDTYPE(INTEGER TYPEID, 
        INTEGER FIELDID, INTEGER FIELD_TYPEIDP)

INTEGER FUNCTION NF_INQ_COMPOUND_FIELDNDIMS(INTEGER NCID, 
        INTEGER XTYPE, INTEGER FIELDID, INTEGER NDIMSP)

INTEGER FUNCTION NF_INQ_COMPOUND_FIELDDIM_SIZES(INTEGER NCID, 
        INTEGER XTYPE, INTEGER FIELDID, INTEGER DIM_SIZES)
@end example

@table @code

@item NCID
The groupid where this compound type exists.

@item XTYPE
The typeid for this compound type, as returned by NF_DEF_COMPOUND, or
NF_INQ_VAR.

@item FIELDID
A one-based index number specifying a field in the compound type.

@item NAME
A character array which will get the name of the field. The name will
be NF_MAX_NAME characters, at most.

@item OFFSETP
An integer which will get the offset of the field.

@item FIELD_TYPEID
An integer which will get the typeid of the field.

@item NDIMSP
An integer which will get the number of dimensions of the field.

@item DIM_SIZESP
An integer array which will get the dimension sizes of the field.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPEID
Bad type id. 

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/fst_types.F.

@example
C     Check the first field of the compound type.
      retval = nf_inq_compound_field(ncid, typeids(1), 1, name_in, 
     &     offset_in, field_typeid_in, ndims_in, dim_sizes_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (name_in(1:len(u_name)) .ne. u_name .or. offset_in .ne. 0 .or.
     &     field_typeid_in .ne. NF_INT .or. ndims_in .ne. 0) stop 2
      retval = nf_inq_compound_fieldname(ncid, typeids(1), 1, name_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (name_in(1:len(u_name)) .ne. u_name) stop 2
      retval = nf_inq_compound_fieldoffset(ncid, typeids(1), 1, 
     &     offset_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (offset_in .ne. 0) stop 2
      retval = nf_inq_compound_fieldtype(ncid, typeids(1), 1, 
     &     field_typeid_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (field_typeid_in .ne. NF_INT) stop 2
      retval = nf_inq_compound_fieldndims(ncid, typeids(1), 1, 
     &     ndims_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (ndims_in .ne. 0) stop 2
@end example

@node Variable Length Array, Opaque Type, Compound Types, User Defined Data Types
@section Variable Length Array Introduction
@cindex variable length arrays
@cindex VLEN

NetCDF-4 added support for a variable length array type. This is not
supported in classic or 64-bit offset files, or in netCDF-4 files
which were created with the NF_CLASSIC_MODEL flag.

A variable length array is represented in C as a structure from HDF5,
the nf_vlen_t structure. It contains a len member, which contains the
length of that array, and a pointer to the array.

So an array of VLEN in C is an array of nc_vlen_t structures. The only
way to handle this in Fortran is with a character buffer sized
correctly for the platform.

The extra access functions NF_GET_VLEN_ELEMENT and NF_PUT_VLEN_ELEMENT
to get and put one VLEN element. (That is, one array of variable
length.) When calling the put, the data are not copied from the
source. When calling the get the data are copied from VLEN allocated
memory, which must still be freed (see below).

VLEN arrays are handled differently with respect to allocation of
memory. Generally, when reading data, it is up to the user to malloc
(and subsequently free) the memory needed to hold the data. It is up to
the user to ensure that enough memory is allocated.

With VLENs, this is impossible. The user cannot know the size of an
array of VLEN until after reading the array. Therefore when reading
VLEN arrays, the netCDF library will allocate the memory for the data within
each VLEN.

It is up to the user, however, to eventually free this memory. This is
not just a matter of one call to free, with the pointer to the array
of VLENs; each VLEN contains a pointer which must be freed.

Compression is permitted but may not be effective for VLEN data,
because the compression is applied to the nc_vlen_t structures, rather
than the actual data.

@menu
* NF_DEF_VLEN::                 
* NF_INQ_VLEN::                 
* NF_FREE_VLEN::                
* NF_PUT_VLEN_ELEMENT::         
* NF_GET_VLEN_ELEMENT::         
@end menu

@node NF_DEF_VLEN, NF_INQ_VLEN, Variable Length Array, Variable Length Array
@subsection Define a Variable Length Array (VLEN): NF_DEF_VLEN
@findex NF_DEF_VLEN
@cindex VLEN, defining

Use this function to define a variable length array type. 

@heading Usage

@example
INTEGER FUNCTION NF_DEF_VLEN(INTEGER NCID, CHARACTER*(*) NAME, 
        INTEGER BASE_TYPEID, INTEGER XTYPEP)
@end example

@table @code

@item NCID
The ncid of the file to create the VLEN type in.

@item NAME 
A name for the VLEN type.

@item BASE_TYPEID
The typeid of the base type of the VLEN. For example, for a VLEN of
shorts, the base type is NF_SHORT. This can be a user defined type.

@item XTYPEP
The typeid of the new VLEN type will be set here.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EMAXNAME
NF_MAX_NAME exceeded.

@item NF_ENAMEINUSE
Name is already in use.

@item NF_EBADNAME
Attribute or variable name contains illegal characters.

@item NF_EBADID
ncid invalid.

@item NF_EBADGRPID
Group ID part of ncid was invalid.

@item NF_EINVAL
Size is invalid.

@item NF_ENOMEM
Out of memory.

@end table

@heading Example

This example is from nf_test/ftst_vars4.F.

@example
C     Create the vlen type.
      retval = nf_def_vlen(ncid, vlen_type_name, nf_int, vlen_typeid)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_VLEN, NF_FREE_VLEN, NF_DEF_VLEN, Variable Length Array
@subsection Learning about a Variable Length Array (VLEN) Type: NF_INQ_VLEN
@findex NF_DEF_VLEN
@cindex VLEN, defining

Use this type to learn about a vlen.

@heading Usage

@example
INTEGER FUNCTION NF_INQ_VLEN(INTEGER NCID, INTEGER XTYPE,
        CHARACTER*(*) NAME, INTEGER DATUM_SIZEP, INTEGER  
        BASE_NF_TYPEP)
@end example

@table @code

@item NCID
The ncid of the file that contains the VLEN type.

@item XTYPE
The type of the VLEN to inquire about.

@item NAME
The name of the VLEN type. The name will be NF_MAX_NAME characters or
less.

@item DATUM_SIZEP
A pointer to a size_t, this will get the size of one element of this
vlen.

@item BASE_NF_TYPEP
An integer that will get the type of the VLEN base type. (In other
words, what type is this a VLEN of?)

@end table


@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPE
Can't find the typeid.

@item NF_EBADID
ncid invalid.

@item NF_EBADGRPID
Group ID part of ncid was invalid.

@end table

@heading Example

This example is from nf_test/ftst_vars4.F.

@example
C     Use nf_inq_vlen and make sure we get the same answers as we did
C     with nf_inq_user_type.
      retval = nf_inq_vlen(ncid, typeids(1), type_name, base_size, 
     &     base_type)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_FREE_VLEN, NF_PUT_VLEN_ELEMENT, NF_INQ_VLEN, Variable Length Array
@subsection Releasing Memory for a Variable Length Array (VLEN) Type: NF_FREE_VLEN
@findex NF_FREE_VLEN
@cindex VLEN, defining

When a VLEN is read into user memory from the file, the HDF5 library
performs memory allocations for each of the variable length arrays
contained within the VLEN structure. This memory must be freed by the
user to avoid memory leaks.

This violates the normal netCDF expectation that the user is
responsible for all memory allocation. But, with VLEN arrays, the
underlying HDF5 library allocates the memory for the user, and the user
is responsible for deallocating that memory.

@heading Usage

@example
INTEGER FUNCTION NF_FREE_VLEN(CHARACTER VL);
@end example

@table @code

@item VL
The variable length array structure which is to be freed.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPE
Can't find the typeid.

@end table

@heading Example

@example
@end example

@node NF_PUT_VLEN_ELEMENT, NF_GET_VLEN_ELEMENT, NF_FREE_VLEN, Variable Length Array
@subsection Set a Variable Length Array with NF_PUT_VLEN_ELEMENT
@findex NF_PUT_VLEN_ELEMENT

Use this to set the element of the (potentially) n-dimensional array
of VLEN. That is, this sets the data in one variable length array.

@heading Usage

@example
INTEGER FUNCTION NF_PUT_VLEN_ELEMENT(INTEGER NCID, INTEGER XTYPE,
        CHARACTER*(*) VLEN_ELEMENT, INTEGER LEN, DATA)
@end example

@table @code

@item NCID
The ncid of the file that contains the VLEN type.

@item XTYPE
The type of the VLEN.

@item VLEN_ELEMENT
The VLEN element to be set.

@item LEN
The number of entries in this array.

@item DATA
The data to be stored. Must match the base type of this VLEN.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPE
Can't find the typeid.

@item NF_EBADID
ncid invalid.

@item NF_EBADGRPID
Group ID part of ncid was invalid.

@end table

@heading Example

This example is from nf_test/ftst_vars4.F.

@example
C     Set up the vlen with this helper function, since F77 can't deal
C     with pointers.
      retval = nf_put_vlen_element(ncid, vlen_typeid, vlen, 
     &     vlen_len, data1)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_GET_VLEN_ELEMENT,  , NF_PUT_VLEN_ELEMENT, Variable Length Array
@subsection Set a Variable Length Array with NF_GET_VLEN_ELEMENT
@findex NF_GET_VLEN_ELEMENT

Use this to set the element of the (potentially) n-dimensional array
of VLEN. That is, this sets the data in one variable length array.

@heading Usage

@example
INTEGER FUNCTION NF_GET_VLEN_ELEMENT(INTEGER NCID, INTEGER XTYPE,
        CHARACTER*(*) VLEN_ELEMENT, INTEGER LEN, DATA)
@end example

@table @code

@item NCID
The ncid of the file that contains the VLEN type.

@item XTYPE
The type of the VLEN.

@item VLEN_ELEMENT
The VLEN element to be set.

@item LEN
This will be set to the number of entries in this array.

@item DATA
The data will be copied here. Sufficient storage must be available or
bad things will happen to you.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPE
Can't find the typeid.

@item NF_EBADID
ncid invalid.

@item NF_EBADGRPID
Group ID part of ncid was invalid.

@end table

@heading Example

This example is from nf_test/ftst_vars4.F.

@example
C     Read the vlen attribute.
      retval = nf_get_att(ncid, NF_GLOBAL, 'att1', vlen_in)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Get the data from the vlen we just read.
      retval = nf_get_vlen_element(ncid, vlen_typeid, vlen_in, 
     &     vlen_len_in, data1_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node Opaque Type, Enum Type, Variable Length Array, User Defined Data Types
@section Opaque Type Introduction
@cindex opaque type

NetCDF-4 added support for the opaque type. This is not supported in
classic or 64-bit offset files.

The opaque type is a type which is a collection of objects of a known
size. (And each object is the same size). Nothing is known to netCDF
about the contents of these blobs of data, except their size in bytes,
and the name of the type.

To use an opaque type, first define it with @ref{NF_DEF_OPAQUE}. If
encountering an enum type in a new data file, use @ref{NF_INQ_OPAQUE}
to learn its name and size.

@menu
* NF_DEF_OPAQUE::               
* NF_INQ_OPAQUE::               
@end menu

@node NF_DEF_OPAQUE, NF_INQ_OPAQUE, Opaque Type, Opaque Type
@subsection Creating Opaque Types: NF_DEF_OPAQUE
@findex NF_DEF_OPAQUE

Create an opaque type. Provide a size and a name.

@heading Usage 

@example
INTEGER FUNCTION NF_DEF_OPAQUE(INTEGER NCID, INTEGER SIZE, 
        CHARACTER*(*) NAME, INTEGER TYPEIDP)
@end example

@table @code

@item NCID
The groupid where the type will be created. The type may be used
anywhere in the file, no matter what group it is in.

@item SIZE
The size of each opaque object.

@item NAME
The name for this type. Must be shorter than NF_MAX_NAME.

@item TYPEIDP
Pointer where the new typeid for this type is returned. Use this
typeid when defining variables of this type with @ref{NF_DEF_VAR}.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPEID
Bad typeid.

@item NF_EBADFIELDID
Bad fieldid.

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_vars3.F.

@example
C     Create the opaque type.
      retval = nf_def_opaque(ncid, opaque_size, opaque_type_name, 
     &     opaque_typeid)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@menu
* NF_INQ_OPAQUE::               
@end menu

@node NF_INQ_OPAQUE,  , NF_DEF_OPAQUE, Opaque Type
@subsection Learn About an Opaque Type: NF_INQ_OPAQUE
@findex NF_INQ_OPAQUE

Given a typeid, get the information about an opaque type.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_OPAQUE(INTEGER NCID, INTEGER XTYPE,
        CHARACTER*(*) NAME, INTEGER SIZEP)
@end example

@table @code

@item NCID
The ncid for the group containing the opaque type.

@item XTYPE
The typeid for this opaque type, as returned by NF_DEF_COMPOUND, or
NF_INQ_VAR.

@item NAME
The name of the opaque type will be copied here. It will
be NF_MAX_NAME bytes or less.

@item SIZEP
The size of the opaque type will be copied here.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPEID
Bad typeid.

@item NF_EBADFIELDID
Bad fieldid.

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_vars3.F.

@example
C     Use nf_inq_opaque and make sure we get the same answers as we did
C     with nf_inq_user_type.
      retval = nf_inq_opaque(ncid, typeids(2), type_name, base_size)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node Enum Type,  , Opaque Type, User Defined Data Types
@section Enum Type Introduction
@cindex enum type

NetCDF-4 added support for the enum type. This is not supported in
classic or 64-bit offset files.

@menu
* NF_DEF_ENUM::                 
* NF_INSERT_ENUM::              
* NF_INQ_ENUM::                 
* NF_INQ_ENUM_MEMBER::          
* NF_INQ_ENUM_IDENT::           
@end menu

@node NF_DEF_ENUM, NF_INSERT_ENUM, Enum Type, Enum Type
@subsection Creating a Enum Type: NF_DEF_ENUM
@findex NF_DEF_ENUM

Create an enum type. Provide an ncid, a name, and a base integer
type. 

After calling this function, fill out the type with repeated calls to
NF_INSERT_ENUM (@pxref{NF_INSERT_ENUM}). Call NF_INSERT_ENUM once for
each value you wish to make part of the enumeration.

@heading Usage 

@example
INTEGER FUNCTION NF_DEF_ENUM(INTEGER NCID, INTEGER BASE_TYPEID, 
        CHARACTER*(*) NAME, INTEGER TYPEIDP)
@end example

@table @code

@item NCID
The groupid where this compound type will be created.

@item BASE_TYPEID
The base integer type for this enum. Must be one of: NF_BYTE,
NF_UBYTE, NF_SHORT, NF_USHORT, NF_INT, NF_UINT, NF_INT64, NF_UINT64.

@item NAME
The name of the new enum type.

@item TYPEIDP
The typeid of the new type will be placed here.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENAMEINUSE
That name is in use. Compound type names must be unique in the data
file. 

@item NF_EMAXNAME
Name exceeds max length NF_MAX_NAME.

@item NF_EBADNAME
Name contains illegal characters.

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag NF_NETCDF4. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@item NF_EPERM
Attempt to write to a read-only file.

@item NF_ENOTINDEFINE
Not in define mode.

@end table

This example is from nf_test/ftst_vars3.F.

@example
C     Create the enum type.
      retval = nf_def_enum(ncid, NF_INT, enum_type_name, enum_typeid)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INSERT_ENUM, NF_INQ_ENUM, NF_DEF_ENUM, Enum Type
@subsection Inserting a Field into a Enum Type: NF_INSERT_ENUM
@findex NF_INSERT_ENUM

Insert a named member into a enum type.

@heading Usage 

@example
INTEGER FUNCTION NF_INSERT_ENUM(INTEGER NCID, INTEGER XTYPE, 
        CHARACTER IDENTIFIER, INTEGER VALUE)
@end example

@table @code

@item NCID
The ncid of the group which contains the type.

@item TYPEID
The typeid for this enum type, as returned by nf_def_enum, or
nf_inq_var.

@item IDENTIFIER
The identifier of the new member.

@item VALUE
The value that is to be associated with this member.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADID
Bad group id. 

@item NF_ENAMEINUSE
That name is in use. Field names must be unique within a enum type.

@item NF_EMAXNAME
Name exceed max length NF_MAX_NAME.

@item NF_EBADNAME
Name contains illegal characters.

@item NF_ENOTNC4
Attempting a netCDF-4 operation on a netCDF-3 file. NetCDF-4
operations can only be performed on files defined with a create mode
which includes flag NF_NETCDF4. (@pxref{NF_OPEN}).

@item NF_ESTRICTNC3
This file was created with the strict netcdf-3 flag, therefore
netcdf-4 operations are not allowed. (@pxref{NF_OPEN}).

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@item NF_ENOTINDEFINE
Not in define mode.

@end table

@heading Example

This example is from nf_test/ftst_vars3.F.

@example
      one = 1
      zero = 0
      retval = nf_insert_enum(ncid, enum_typeid, zero_name, zero)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_insert_enum(ncid, enum_typeid, one_name, one)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_ENUM, NF_INQ_ENUM_MEMBER, NF_INSERT_ENUM, Enum Type
@subsection Learn About a Enum Type: NF_INQ_ENUM
@findex NF_INQ_ENUM

Get information about a user-defined enumeration type.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_ENUM(INTEGER NCID, INTEGER XTYPE,
        CHARACTER*(*) NAME, INTEGER BASE_NF_TYPE, INTEGER BASE_SIZE, 
        INTEGER NUM_MEMBERS)
@end example

@table @code

@item NCID
The group ID of the group which holds the enum type.

@item XTYPE
The typeid for this enum type, as returned by NF_DEF_ENUM, or
NF_INQ_VAR.

@item NAME
Character array which will get the name. It will have a maximum length
of NF_MAX_NAME.

@item BASE_NF_TYPE
An integer which will get the base integer type of this enum.

@item BASE_SIZE
An integer which will get the size (in bytes) of the base integer type
of this enum.

@item NUM_MEMBERS
An integer which will get the number of members defined for this
enumeration type.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPEID
Bad type id. 

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

In this example from nf_test/ftst_vars3.F, an enum type is created and
then examined:

@example
      retval = nf_inq_enum(ncid, typeids(1), type_name, base_type, 
     &     base_size, num_members)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (base_type .ne. NF_INT .or. num_members .ne. 2) stop 2
@end example

@node NF_INQ_ENUM_MEMBER, NF_INQ_ENUM_IDENT, NF_INQ_ENUM, Enum Type
@subsection Learn the Name of a Enum Type: nf_inq_enum_member
@findex nf_inq_enum_member

Get information about a member of an enum type.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_ENUM_MEMBER(INTEGER NCID, INTEGER XTYPE, 
        INTEGER IDX, CHARACTER*(*) NAME, INTEGER VALUE)
@end example

@table @code

@item NCID
The groupid where this enum type exists.

@item XTYPE
The typeid for this enum type.

@item IDX
The one-based index number for the member of interest. 

@item NAME
A character array which will get the name of the member. It will have
a maximum length of NF_MAX_NAME.

@item VALUE
An integer that will get the value associated with this member.

@end table

@heading Errors

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPEID
Bad type id. 

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@end table

@heading Example

This example is from nf_test/ftst_vars3.F:

@example
C     Check the members of the enum type.
      retval = nf_inq_enum_member(ncid, typeids(1), 1, member_name, 
     &     member_value)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (member_name(1:len(zero_name)) .ne. zero_name .or.
     &     member_value .ne. 0) stop 2
      retval = nf_inq_enum_member(ncid, typeids(1), 2, member_name, 
     &     member_value)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (member_name(1:len(one_name)) .ne. one_name .or.
     &     member_value .ne. 1) stop 2
@end example

@node NF_INQ_ENUM_IDENT,  , NF_INQ_ENUM_MEMBER, Enum Type
@subsection Learn the Name of a Enum Type: NF_INQ_ENUM_IDENT
@findex NF_INQ_ENUM_IDENT

Get the name which is associated with an enum member value.

This is similar to NF_INQ_ENUM_MEMBER, but instead of using the index
of the member, you use the value of the member.

@heading Usage 

@example
INTEGER FUNCTION NF_INQ_ENUM_IDENT(INTEGER NCID, INTEGER XTYPE,
        INTEGER VALUE, CHARACTER*(*) IDENTIFIER)
@end example

@table @code

@item NCID
The groupid where this enum type exists.

@item XTYPE
The typeid for this enum type.

@item VALUE
The value for which an identifier is sought.

@item IDENTIFIER
A character array that will get the identifier. It will have a maximum
length of NF_MAX_NAME.

@end table

@heading Return Code

@table @code

@item NF_NOERR
No error.

@item NF_EBADTYPEID
Bad type id, or not an enum type.

@item NF_EHDFERR
An error was reported by the HDF5 layer.

@item NF_EINVAL
The value was not found in the enum.

@end table

@heading Example

In this example from nf_test/ftst_vars3.F, the values for 0 and 1 are
checked in an enum.

@example
      retval = nf_inq_enum_ident(ncid, typeids(1), 0, member_name)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (member_name(1:len(zero_name)) .ne. zero_name) stop 2
      retval = nf_inq_enum_ident(ncid, typeids(1), 1, member_name)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (member_name(1:len(one_name)) .ne. one_name) stop 2
@end example

@node Variables, Attributes, User Defined Data Types, Top
@chapter Variables

@menu
* Variables Introduction::      
* Variable Types::              
* NF_DEF_VAR::                  Create a Variable
* NF_DEF_VAR_CHUNKING::         
* NF_INQ_VAR_CHUNKING::         
* NF_SET_VAR_CHUNK_CACHE::      
* NF_GET_VAR_CHUNK_CACHE::      
* NF_DEF_VAR_FILL::             
* NF_INQ_VAR_FILL::             
* NF_DEF_VAR_DEFLATE::          
* NF_INQ_VAR_DEFLATE::          
* NF_INQ_VAR_SZIP::             
* NF_DEF_VAR_FLETCHER32::       
* NF_INQ_VAR_FLETCHER32::       
* NF_DEF_VAR_ENDIAN::           
* NF_INQ_VAR_ENDIAN::           
* NF_INQ_VARID::                
* NF_INQ_VAR family::           Get Information about a Variable from Its ID:
* NF_PUT_VAR1_  type::          
* NF_PUT_VAR_ type::            
* NF_PUT_VARA_ type::           
* NF_PUT_VARS_ type::           
* NF_PUT_VARM_ type::           
* NF_GET_VAR1_ type::           
* NF_GET_VAR_ type::            
* NF_GET_VARA_ type::           
* NF_GET_VARS_ type::           
* NF_GET_VARM_ type::           
* Reading and Writing Character String Values::  
* Fill Values::                 What's Written Where there's No Data?
* NF_RENAME_VAR::               
* NF_VAR_PAR_ACCESS::           
@end menu

@node Variables Introduction, Variable Types, Variables, Variables
@section Variables Introduction

Variables for a netCDF dataset are defined when the dataset is
created, while the netCDF dataset is in define mode. Other variables
may be added later by reentering define mode. A netCDF variable has a
name, a type, and a shape, which are specified when it is defined. A
variable may also have values, which are established later in data
mode.

Ordinarily, the name, type, and shape are fixed when the variable is
first defined. The name may be changed, but the type and shape of a
variable cannot be changed. However, a variable defined in terms of
the unlimited dimension can grow without bound in that dimension.

A netCDF variable in an open netCDF dataset is referred to by a small
integer called a variable ID.

Variable IDs reflect the order in which variables were defined within
a netCDF dataset. Variable IDs are 1, 2, 3,..., in the order in which
the variables were defined. A function is available for getting the
variable ID from the variable name and vice-versa.

Attributes (see @ref{Attributes}) may be associated with a variable to
specify such properties as units.

Operations supported on variables are:
@itemize

@item
Create a variable, given its name, data type, and shape. 

@item
Get a variable ID from its name. 

@item
Get a variable's name, data type, shape, and number of attributes from
its ID.

@item
Put a data value into a variable, given variable ID, indices, and
value.

@item
Put an array of values into a variable, given variable ID, corner
indices, edge lengths, and a block of values.

@item
Put a subsampled or mapped array-section of values into a variable,
given variable ID, corner indices, edge lengths, stride vector, index
mapping vector, and a block of values.

@item
Get a data value from a variable, given variable ID and indices. 

@item
Get an array of values from a variable, given variable ID, corner
indices, and edge lengths.

@item
Get a subsampled or mapped array-section of values from a variable,
given variable ID, corner indices, edge lengths, stride vector, and
index mapping vector.

@item
Rename a variable. 
@end itemize

@node Variable Types, NF_DEF_VAR, Variables Introduction, Variables
@section Language Types Corresponding to netCDF external data types

The following table gives the netCDF external data types and the
corresponding type constants for defining variables in the FORTRAN
interface:

@multitable @columnfractions .25 .60 .15
@item Type @tab FORTRAN API Mnemonic @tab Bits

@item byte
@tab NF_BYTE 
@tab 8
 
@item char
@tab NF_CHAR 
@tab 8
 
@item short
@tab NF_SHORT 
@tab 16
 
@item int
@tab NF_INT 
@tab 32
 
@item float
@tab NF_FLOAT 
@tab 32
 
@item double
@tab NF_DOUBLE 
@tab 64
@end multitable
 
The first column gives the netCDF external data type, which is the
same as the CDL data type. The next column gives the corresponding
FORTRAN parameter for use in netCDF functions (the parameters are
defined in the netCDF FORTRAN include-file netcdf.inc). The last
column gives the number of bits used in the external representation of
values of the corresponding type.

Note that there are no netCDF types corresponding to 64-bit integers
or to characters wider than 8 bits in the current version of the
netCDF library.

@node NF_DEF_VAR, NF_DEF_VAR_CHUNKING, Variable Types, Variables
@section Create a Variable: @code{NF_DEF_VAR} 
@findex NF_DEF_VAR

The function NF_DEF_VAR adds a new variable to an open netCDF dataset
in define mode. It returns (as an argument) a variable ID, given the
netCDF ID, the variable name, the variable type, the number of
dimensions, and a list of the dimension IDs.

@heading Usage 
@example
INTEGER FUNCTION NF_DEF_VAR(INTEGER NCID, CHARACTER*(*) NAME,
                            INTEGER XTYPE, INTEGER NVDIMS,
                            INTEGER VDIMS(*), INTEGER varid)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item NAME
Variable name.
 
@item XTYPE
One of the set of predefined netCDF external data types. The type of
this parameter, NF_TYPE, is defined in the netCDF header file. The
valid netCDF external data types are NF_BYTE, NF_CHAR, NF_SHORT,
NF_INT, NF_FLOAT, and NF_DOUBLE. If the file is a NetCDF-4/HDF5 file,
the additional types NF_UBYTE, NF_USHORT, NF_UINT, NF_INT64,
NF_UINT64, and NF_STRING may be used, as well as a user defined type
ID.
 
@item NVDIMS
Number of dimensions for the variable. For example, 2 specifies a
matrix, 1 specifies a vector, and 0 means the variable is a scalar
with no dimensions. Must not be negative or greater than the
predefined constant NF_MAX_VAR_DIMS.
 
@item VDIMS
Vector of ndims dimension IDs corresponding to the variable
dimensions. If the ID of the unlimited dimension is included, it must
be first. This argument is ignored if ndims is 0. For expanded model
netCDF4/HDF5 files, there may be any number of unlimited dimensions,
and they may be used in any element of the dimids array.
 
@item varid
Returned variable ID.

@end table

@heading Errors 

NF_DEF_VAR returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The netCDF dataset is not in define mode. 

@item
The specified variable name is the name of another existing variable. 

@item
The specified type is not a valid netCDF type. 

@item
The specified number of dimensions is negative or more than the
constant NF_MAX_VAR_DIMS, the maximum number of dimensions permitted
for a netCDF variable.

@item
One or more of the dimension IDs in the list of dimensions is not a
valid dimension ID for the netCDF dataset.

@item
The number of variables would exceed the constant NF_MAX_VARS, the
maximum number of variables permitted in a netCDF dataset.

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_DEF_VAR to create a variable named rh of
type double with three dimensions, time, lat, and lon in a new netCDF
dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER  STATUS, NCID
INTEGER  LATDIM, LONDIM, TIMDIM  ! dimension IDs
INTEGER  RHID                    ! variable ID
INTEGER  RHDIMS(3)               ! variable shape
   ... 
STATUS = NF_CREATE ('foo.nc', NF_NOCLOBBER, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
                                 ! define dimensions
STATUS = NF_DEF_DIM(NCID, 'lat', 5, LATDIM)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_DEF_DIM(NCID, 'lon', 10, LONDIM)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_DEF_DIM(NCID, 'time', NF_UNLIMITED, TIMDIM)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
         ... 
                                 ! define variable
RHDIMS(1) = LONDIM
RHDIMS(2) = LATDIM
RHDIMS(3) = TIMDIM
STATUS = NF_DEF_VAR (NCID, 'rh', NF_DOUBLE, 3, RHDIMS, RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_DEF_VAR_CHUNKING, NF_INQ_VAR_CHUNKING, NF_DEF_VAR, Variables
@section Define Chunking Parameters for a Variable: @code{NF_DEF_VAR_CHUNKING}
@findex NF_DEF_VAR_CHUNKING
@cindex chunking
@cindex chunksizes
@cindex variables, chunking
@cindex variables, contiguous
@cindex contiguous

The function NF_DEF_VAR_CHUNKING sets the storage parameters for a
variable in a netCDF-4 file. It can set the chunk sizes to get chunked
storage, or it can set the contiguous flag to get contiguous storage.

Variables that make use of one or more unlimited dimensions,
compression, or checksums must use chunking.  Such variables are
created with default chunk sizes of 1 for each unlimited dimension and
the dimension length for other dimensions, except that if the
resulting chunks are too large, the default chunk sizes for non-record
dimensions are reduced.

The total size of a chunk must be less than 4 GiB. That is, the product
of all chunksizes and the size of the data (or the size of nc_vlen_t
for VLEN types) must be less than 4 GiB.

This function may only be called after the variable is defined, but
before nc_enddef is called.  Once the chunking parameters are set for
a variable, they cannot be changed.  This function can be used to
change the default chunking for record, compressed, or checksummed
variables before nc_enddef is called.

Note that you cannot set chunking for scalar variables. Only non-scalar
variables can have chunking.

@heading Usage 

@example
NF_DEF_VAR_CHUNKING(INTEGER NCID, INTEGER VARID, INTEGER STORAGE, INTEGER CHUNKSIZES)
@end example

@table @code
@item ncid
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item varid
Variable ID.

@item storage
If NF_CONTIGUOUS, then contiguous storage is used for this
variable. Variables with compression, shuffle filter, checksums, or
one or more unlimited dimensions cannot use contiguous storage. If
contiguous storage is turned on, the chunksizes parameter is ignored.

If NF_CHUNKED, then chunked storage is used for this variable.
Chunk sizes may be specified with the chunksizes parameter.
Default sizes will be used if chunking is required and this function
is not called.

By default contiguous storage is used for fix-sized variables when
conpression, chunking, checksums, or endianness control are not used.

@item chunksizes
An array of chunk sizes. The array must have the one chunksize for
each dimension in the variable. If contiguous storage is used, 
then the chunksizes parameter is ignored.
 
@end table

@heading Errors 

NF_DEF_VAR_CHUNKING returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_EINVAL
Invalid input. This can occur when the user attempts to set contiguous
storage for a variable with compression or checksums, or one or more
unlimited dimensions.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@item NF_ELATEDEF
This variable has already been the subject of a NF_ENDDEF call. In
netCDF-4 files NF_ENDDEF will be called automatically for any data
read or write. Once enddef has been called, it is impossible to set
the chunking for a variable.

@item NF_ENOTINDEFINE
Not in define mode. This is returned for netCDF classic or 64-bit
offset files, or for netCDF-4 files, when they were been created with
NF_STRICT_NC3 flag. (@pxref{NF_CREATE}).

@item NF_ESTRICTNC3
Trying to create a var some place other than the root group in a
netCDF file with NF_STRICT_NC3 turned on.

@end table

@heading Example

In this example from nf_test/ftst_vars.F, a file is created, two
dimensions and a variable are defined, and the chunksizes of the data
are set to the size of the data (that is, data will be written in one
chunk).

@example
C     Create the netCDF file.
      retval = nf_create(FILE_NAME, NF_NETCDF4, ncid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Define the dimensions.
      retval = nf_def_dim(ncid, "x", NX, x_dimid)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_def_dim(ncid, "y", NY, y_dimid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Define the variable. 
      dimids(1) = y_dimid
      dimids(2) = x_dimid
      retval = NF_DEF_VAR(ncid, "data", NF_INT, NDIMS, dimids, varid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Turn on chunking.
      chunks(1) = NY
      chunks(2) = NX
      retval = NF_DEF_VAR_chunking(ncid, varid, NF_CHUNKED, chunks)
      if (retval .ne. nf_noerr) call handle_err(retval)

@end example

@node NF_INQ_VAR_CHUNKING, NF_SET_VAR_CHUNK_CACHE, NF_DEF_VAR_CHUNKING, Variables
@section Learn About Chunking Parameters for a Variable: @code{NF_INQ_VAR_CHUNKING}
@findex NF_INQ_VAR_CHUNKING

The function NF_INQ_VAR_CHUNKING returns the chunking settings for a
variable in a netCDF-4 file. 

@heading Usage 

@example
NF_INQ_VAR_CHUNKING(INTEGER NCID, INTEGER VARID, INTEGER STORAGE, INTEGER CHUNKSIZES);
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item STORAGE
On return, set to NF_CONTIGUOUS if this variable uses contiguous
storage, NF_CHUNKED if it uses chunked storage.

@item CHUNKSIZES
An array of chunk sizes.  The length of CHUNKSIZES must be the same as
the number of dimensions of the variable.

@end table

@heading Errors 

NF_INQ_VAR_CHUNKING returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@end table

@heading Example

In this example from nf_test/ftst_vars.F, a variable with chunked
storage is checked to ensure that the chunksizes are set to expected
values.

@example
C     Is everything set that is supposed to be?
      retval = nf_inq_var_chunking(ncid, varid, storage, chunks_in)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (storage .ne. NF_CHUNKED) stop 2
      if (chunks(1) .ne. chunks_in(1)) stop 2
      if (chunks(2) .ne. chunks_in(2)) stop 2
@end example

@node NF_SET_VAR_CHUNK_CACHE, NF_GET_VAR_CHUNK_CACHE, NF_INQ_VAR_CHUNKING, Variables
@section Set HDF5 Chunk Cache for a Variable: NF_SET_VAR_CHUNK_CACHE
@findex NF_SET_VAR_CHUNK_CACHE
@cindex HDF5 chunk cache, per-variable

This function changes the chunk cache settings for a variable. The
change in cache size happens immediately. This is a property of the
open file - it does not persist the next time you open the file.

For more information, see the documentation for the H5Pset_cache()
function in the HDF5 library at the HDF5 website:
@uref{@value{hdf5-url}}.

@heading Usage 

@example
NF_SET_VAR_CHUNK_CACHE(INTEGER NCID, INTEGER VARID, INTEGER SIZE, INTEGER NELEMS, 
		       INTEGER PREEMPTION);
@end example

@table @code

@item NCID
NetCDF ID, from a previous call to nc_open or nc_create.
 
@item VARID
Variable ID.

@item SIZE
The total size of the raw data chunk cache, in megabytes. This should be
big enough to hold multiple chunks of data. (Note that the C API uses
bytes, but the Fortran APIs uses megabytes to avoid numbers that can't
fit in 4-byte integers.)

@item NELEMS
The number of chunk slots in the raw data chunk cache hash table. This
should be a prime number larger than the number of chunks that will be
in the cache.

@item PREEMPTION
The preemption value must be between 0 and 100 inclusive and indicates
the degreee to which chunks that have been fully read are favored for
kicking out of the chunk cache, when needed. A value of zero means
fully read chunks are treated no differently than other chunks (the
preemption is strictly Least Recently Used) while a value of 100 means
fully read chunks are always preempted before other chunks. (The C API
uses a float between 0 and 1 for this value).

@end table

@heading Return Codes

@table @code

@item NF_NOERR
No error.

@item NF_EINVAL
Preemption must be between zero and 100 (inclusive). 

@end table

@heading Example 

This example is from nf_test/ftst_vars2.F:

@example
      include 'netcdf.inc'
 ...
C     These will be used to set the per-variable chunk cache.
      integer CACHE_SIZE, CACHE_NELEMS, CACHE_PREEMPTION
      parameter (CACHE_SIZE = 8, CACHE_NELEMS = 571)
      parameter (CACHE_PREEMPTION = 42)
...
C        Set variable caches.
         retval = nf_set_var_chunk_cache(ncid, varid(i), CACHE_SIZE, 
     &        CACHE_NELEMS, CACHE_PREEMPTION)
         if (retval .ne. nf_noerr) call handle_err(retval)

@end example

@node NF_GET_VAR_CHUNK_CACHE, NF_DEF_VAR_FILL, NF_SET_VAR_CHUNK_CACHE, Variables
@section Get the HDF5 Chunk Cache Settings for a variable: NF_GET_VAR_CHUNK_CACHE
@findex nf_get_chunk_cache
@cindex HDF5 chunk cache

This function gets the current chunk cache settings for a variable in
a netCDF-4/HDF5 file.

For more information, see the documentation for the H5Pget_cache()
function in the HDF5 library at the HDF5 website:
@uref{@value{hdf5-url}}.

@heading Usage 

@example
INTEGER NF_GET_VAR_CHUNK_CACHE(INTEGER NCID, INTEGER VARID, INTEGER SIZE, INTEGER NELEMS, 
                               INTEGER PREEMPTION);
@end example

@table @code

@item ncid
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item varid
Variable ID.

@item sizep
The total size of the raw data chunk cache, in megabytes, will be put
here.

@item nelemsp
The number of chunk slots in the raw data chunk cache hash table will
be put here. 

@item preemptionp
The preemption will be put here.  The preemtion value is between 0 and
100 inclusive and indicates how much chunks that have been fully read
are favored for preemption.  A value of zero means fully read chunks
are treated no differently than other chunks (the preemption is
strictly LRU) while a value of 100 means fully read chunks are always
preempted before other chunks.  

@end table

@heading Return Codes

@table @code

@item NC_NOERR
No error.

@end table

@heading Example 

This example is from nf_test/ftst_vars2.c:

@example
      include 'netcdf.inc'
...
C     These will be used to set the per-variable chunk cache.
      integer CACHE_SIZE, CACHE_NELEMS, CACHE_PREEMPTION
      parameter (CACHE_SIZE = 8, CACHE_NELEMS = 571)
      parameter (CACHE_PREEMPTION = 42)

C     These will be used to check the setting of the per-variable chunk
C     cache.
      integer cache_size_in, cache_nelems_in, cache_preemption_in

...
         retval = nf_get_var_chunk_cache(ncid, varid(i), cache_size_in, 
     &        cache_nelems_in, cache_preemption_in)
         if (retval .ne. nf_noerr) call handle_err(retval)
         if (cache_size_in .ne. CACHE_SIZE .or. cache_nelems_in .ne. 
     &        CACHE_NELEMS .or. cache_preemption .ne. CACHE_PREEMPTION)
     &        stop 8

@end example

@node NF_DEF_VAR_FILL, NF_INQ_VAR_FILL, NF_GET_VAR_CHUNK_CACHE, Variables
@section Define Fill Parameters for a Variable: @code{nf_def_var_fill}
@findex NF_DEF_VAR_FILL
@cindex fill
@cindex variables, fill

The function NF_DEF_VAR_FILL sets the fill parameters for a
variable in a netCDF-4 file. 

This function must be called after the variable is defined, but before
NF_ENDDEF is called.

@heading Usage 

@example
NF_DEF_VAR_FILL(INTEGER NCID, INTEGER VARID, INTEGER NO_FILL, FILL_VALUE);
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item NO_FILL
Set to non-zero value to set no_fill mode on a variable. When this
mode is on, fill values will not be written for the variable. This is
helpful in high performance applications. For netCDF-4/HDF5 files
(whether classic model or not), this may only be changed after the
variable is defined, but before it is committed to disk (i.e. before
the first NF_ENDDEF after the NF_DEF_VAR.) For classic and 64-bit
offset file, the no_fill mode may be turned on and off at any time.

@item FILL_VALUE
A value which will be used as the fill value for the variable. Must be
the same type as the variable. This will be written to a _FillValue
attribute, created for this purpose. If NULL, this argument will be
ignored.
 
@end table

@heading Return Codes

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@item NF_ELATEDEF
This variable has already been the subject of a NF_ENDDEF call. In
netCDF-4 files NF_ENDDEF will be called automatically for any data
read or write. Once enddef has been called, it is impossible to set
the fill for a variable.

@item NF_ENOTINDEFINE
Not in define mode. This is returned for netCDF classic or 64-bit
offset files, or for netCDF-4 files, when they were been created with
NF_STRICT_NC3 flag. (@pxref{NF_CREATE}).

@item NF_EPERM
Attempt to create object in read-only file.

@end table

@heading Example

@example
@end example

@node NF_INQ_VAR_FILL, NF_DEF_VAR_DEFLATE, NF_DEF_VAR_FILL, Variables
@section Learn About Fill Parameters for a Variable: @code{NF_INQ_VAR_FILL}
@findex NF_INQ_VAR_FILL

The function NF_INQ_VAR_FILL returns the fill settings for a
variable in a netCDF-4 file. 

@heading Usage 

@example
NF_INQ_VAR_FILL(INTEGER NCID, INTEGER VARID, INTEGER NO_FILL, FILL_VALUE)
@end example

@table @code

@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item NO_FILL
An integer which will get a 1 if no_fill mode is set for this
variable, and a zero if it is not set

@item FILL_VALUE
This will get the fill value for this variable. This
parameter will be ignored if it is NULL.

@end table

@heading Return Codes

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@end table

@heading Example

@example
@end example

@node NF_DEF_VAR_DEFLATE, NF_INQ_VAR_DEFLATE, NF_INQ_VAR_FILL, Variables
@section Define Compression Parameters for a Variable: @code{NF_DEF_VAR_DEFLATE}
@findex NF_DEF_VAR_DEFLATE
@cindex deflate
@cindex variables, setting deflate
@cindex compression, setting parameters

The function NF_DEF_VAR_DEFLATE sets the deflate parameters for a
variable in a netCDF-4 file. 

When using parallel I/O for writing data, deflate cannot be used. This
is because the compression makes it impossible for the HDF5 library to
exactly map the data to disk location.

(Deflated data can be read with parallel I/O).

NF_DEF_VAR_DEFLATE must be called after the variable is defined, but before
NF_ENDDEF is called.

@heading Usage 

@example
NF_DEF_VAR_DEFLATE(INTEGER NCID, INTEGER VARID, INTEGER SHUFFLE, INTEGER DEFLATE, 
                   INTEGER DEFLATE_LEVEL);
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item SHUFFLE
If non-zero, turn on the shuffle filter.

@item DEFLATE
If non-zero, turn on the deflate filter at the level specified by the
deflate_level parameter.

@item DEFLATE_LEVEL
Must be between 0 (no deflate, the default) and 9 (slowest, but
``best'' deflate). 

If set to zero, no deflation takes place and the def_var_deflate call
is ignored. This is slightly different from HDF5 handing of 0
deflate, which turns on the filter but makes only trivial changes to
the data.

Informal testing at NetCDF World Headquarters suggests that there is
little to be gained (with the limited set of test data used here), in
setting the deflate level above 2 or 3.
 
@end table

@heading Errors 

NF_DEF_VAR_DEFLATE returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@item NF_ELATEDEF
This variable has already been the subject of a NF_ENDDEF call. In
netCDF-4 files NF_ENDDEF will be called automatically for any data
read or write. Once enddef has been called, it is impossible to set
the deflate for a variable.

@item NF_ENOTINDEFINE
Not in define mode. This is returned for netCDF classic or 64-bit
offset files, or for netCDF-4 files, when they were been created with
NF_STRICT_NC3 flag. (@pxref{NF_CREATE}).

@item NF_EPERM
Attempt to create object in read-only file.

@item NF_EINVAL
Invalid deflate_level. The deflate level must be between 0 and 9,
inclusive.

@end table

@heading Example

In this example from nf_test/ftst_vars.F, a file is created with two
dimensions and one variable. Chunking, deflate, and the fletcher32
filter are turned on. The deflate level is set to 4 below.

@example
C     Create the netCDF file.
      retval = nf_create(FILE_NAME, NF_NETCDF4, ncid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Define the dimensions.
      retval = nf_def_dim(ncid, "x", NX, x_dimid)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_def_dim(ncid, "y", NY, y_dimid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Define the variable. 
      dimids(1) = y_dimid
      dimids(2) = x_dimid
      retval = NF_DEF_VAR(ncid, "data", NF_INT, NDIMS, dimids, varid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Turn on chunking.
      chunks(1) = NY
      chunks(2) = NX
      retval = NF_DEF_VAR_CHUNKING(ncid, varid, NF_CHUNKED, chunks)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Turn on deflate compression, fletcher32 checksum.
      retval = NF_DEF_VAR_deflate(ncid, varid, 0, 1, 4)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = NF_DEF_VAR_FLETCHER32(ncid, varid, NF_FLETCHER32)
      if (retval .ne. nf_noerr) call handle_err(retval)

@end example

@node NF_INQ_VAR_DEFLATE, NF_INQ_VAR_SZIP, NF_DEF_VAR_DEFLATE, Variables
@section Learn About Deflate Parameters for a Variable: @code{NF_INQ_VAR_DEFLATE}
@findex NF_INQ_VAR_DEFLATE

The function NF_INQ_VAR_DEFLATE returns the deflate settings for a
variable in a netCDF-4 file. 

It is not necessary to know the deflate settings to read the
variable. (Deflate is completely transparent to readers of the data).

@heading Usage 

@example
NF_INQ_VAR_DEFLATE(INTEGER NCID, INTEGER VARID, INTEGER SHUFFLE, 
                   INTEGER DEFLATE, INTEGER DEFLATE_LEVEL);
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item SHUFFLE
NF_INQ_VAR_DEFLATE will set this to a 1 if the shuffle filter is
turned on for this variable, and a 0 otherwise.

@item DEFLATE
NF_INQ_VAR_DEFLATE will set this to a 1 if the deflate filter is
turned on for this variable, and a 0 otherwise.

@item DEFLATE_LEVEL
NF_INQ_VAR_DEFLATE function will write the deflate_level here, if
deflate is in use.
 
@end table

@heading Errors 

NF_INQ_VAR_DEFLATE returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@end table

@heading Example

In this example code from nf_test/ftst_vars.F, a file with a variable
using deflate is opened, and the deflate level checked.

@example
C     Is everything set that is supposed to be?
      retval = nf_inq_var_deflate(ncid, varid, shuffle, deflate, 
     +     deflate_level)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (shuffle .ne. 0 .or. deflate .ne. 1 .or. 
     +     deflate_level .ne. 4) stop 2

@end example

@node NF_INQ_VAR_SZIP, NF_DEF_VAR_FLETCHER32, NF_INQ_VAR_DEFLATE, Variables
@section Learn About Szip Parameters for a Variable: @code{NF_INQ_VAR_SZIP}
@findex NF_INQ_VAR_SZIP

The function NF_INQ_VAR_SZIP returns the szip settings for a
variable in a netCDF-4 file. 

It is not necessary to know the szip settings to read the
variable. (Szip is completely transparent to readers of the data).

@heading Usage 

@example
NF_INQ_VAR_SZIP(INTEGER NCID, INTEGER VARID, INTEGER OPTION_MASK, 
                        PIXELS_PER_BLOCK);
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item OPTION_MASK
This will be set to the option_mask value.

@item PIXELS_PER_BLOCK
The number of bits per pixel will be put here.

@end table

@heading Errors 

NF_INQ_VAR_SZIP returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@end table

@heading Example

@example
@end example

@node NF_DEF_VAR_FLETCHER32, NF_INQ_VAR_FLETCHER32, NF_INQ_VAR_SZIP, Variables
@section Define Checksum Parameters for a Variable: @code{NF_DEF_VAR_FLETCHER32}
@findex NF_DEF_VAR_FLETCHER32
@cindex fletcher32
@cindex variables, fletcher32
@cindex checksum
@cindex variables, checksum

The function NF_DEF_VAR_FLETCHER32 sets the checksum property for a
variable in a netCDF-4 file. 

This function may only be called after the variable is defined, but before
NF_ENDDEF is called.

@heading Usage 

@example
NF_DEF_VAR_FLETCHER32(INTEGER NCID, INTEGER VARID, INTEGER CHECKSUM);
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item CHECKSUM
If this is NF_FLETCHER32, fletcher32 checksums will be turned on for this
variable.
 
@end table

@heading Errors 

NF_DEF_VAR_FLETCHER32 returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@item NF_ELATEDEF
This variable has already been the subject of a NF_ENDDEF call. In
netCDF-4 files NF_ENDDEF will be called automatically for any data
read or write. Once enddef has been called, it is impossible to set
the checksum property for a variable.

@item NF_ENOTINDEFINE
Not in define mode. This is returned for netCDF classic or 64-bit
offset files, or for netCDF-4 files, when they were been created with
NF_STRICT_NC3 flag. (@pxref{NF_CREATE}).

@item NF_EPERM
Attempt to create object in read-only file.

@end table

@heading Example

In this example from nf_test/ftst_vars.F, the variable in a file has
the Fletcher32 checksum filter turned on.

@example

C     Create the netCDF file.
      retval = nf_create(FILE_NAME, NF_NETCDF4, ncid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Define the dimensions.
      retval = nf_def_dim(ncid, "x", NX, x_dimid)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_def_dim(ncid, "y", NY, y_dimid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Define the variable. 
      dimids(1) = y_dimid
      dimids(2) = x_dimid
      retval = NF_DEF_VAR(ncid, "data", NF_INT, NDIMS, dimids, varid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Turn on chunking.
      chunks(1) = NY
      chunks(2) = NX
      retval = NF_DEF_VAR_CHUNKING(ncid, varid, NF_CHUNKED, chunks)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Turn on deflate compression, fletcher32 checksums.
      retval = NF_DEF_VAR_DEFLATE(ncid, varid, 0, 1, 4)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = NF_DEF_VAR_FLETCHER32(ncid, varid, NF_FLETCHER32)
      if (retval .ne. nf_noerr) call handle_err(retval)

@end example

@node NF_INQ_VAR_FLETCHER32, NF_DEF_VAR_ENDIAN, NF_DEF_VAR_FLETCHER32, Variables
@section Learn About Checksum Parameters for a Variable: @code{NF_INQ_VAR_FLETCHER32}
@findex NF_INQ_VAR_FLETCHER32

The function NF_INQ_VAR_FLETCHER32 returns the checksum settings for a
variable in a netCDF-4 file. 

@heading Usage 

@example
NF_INQ_VAR_FLETCHER32(INTEGER NCID, INTEGER VARID, INTEGER CHECKSUM);
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item CHECKSUM
NF_INQ_VAR_FLETCHER32 will set this to NF_FLETCHER32 if the fletcher32 filter is
turned on for this variable, and NF_NOCHECKSUM if it is not.

@end table

@heading Errors 

NF_INQ_VAR_FLETCHER32 returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@end table

@heading Example

In this example from nf_test/ftst_vars.F the checksum filter is
checked for a file. Since it was turned on for this variable, the
checksum variable is set to NF_FLETCHER32.

@example
      retval = nf_inq_var_fletcher32(ncid, varid, checksum)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (checksum .ne. NF_FLETCHER32) stop 2
@end example

@node NF_DEF_VAR_ENDIAN, NF_INQ_VAR_ENDIAN, NF_INQ_VAR_FLETCHER32, Variables
@section Define Endianness of a Variable: @code{NF_DEF_VAR_ENDIAN}
@findex NF_DEF_VAR_ENDIAN
@cindex endianness
@cindex big-endian
@cindex little-endian
@cindex variables, endian

The function NF_DEF_VAR_ENDIAN sets the endianness for a variable in a
netCDF-4 file.

This function must be called after the variable is defined, but before
NF_ENDDEF is called.

By default, netCDF-4 variables are in native endianness. That is, they
are big-endian on a big-endian machine, and little-endian on a little
endian machine.

In some cases a user might wish to change from native endianness to
either big or little-endianness. This function allows them to do that.

@heading Usage 

@example
NF_DEF_VAR_ENDIAN(INTEGER NCID, INTEGER VARID, INTEGER ENDIAN)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item ENDIAN
Set to NF_ENDIAN_NATIVE for native endianness. (This is the
default). Set to NF_ENDIAN_LITTLE for little endian, or NF_ENDIAN_BIG
for big endian.
 
@end table

@heading Errors 

NF_DEF_VAR_ENDIAN returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@item NF_ELATEDEF
This variable has already been the subject of a NF_ENDDEF call. In
netCDF-4 files NF_ENDDEF will be called automatically for any data
read or write. Once enddef has been called, it is impossible to set
the endianness of a variable.

@item NF_ENOTINDEFINE
Not in define mode. This is returned for netCDF classic or 64-bit
offset files, or for netCDF-4 files, when they were been created with
NF_STRICT_NC3 flag, and the file is not in define
mode. (@pxref{NF_CREATE}).

@item NF_EPERM
Attempt to create object in read-only file.

@end table

@heading Example

In this example from nf_test/ftst_vars.c, a file is created with one
variable, and its endianness is set to NF_ENDIAN_BIG.

@example
C     Create the netCDF file.
      retval = nf_create(FILE_NAME, NF_NETCDF4, ncid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Define the dimensions.
      retval = nf_def_dim(ncid, "x", NX, x_dimid)
      if (retval .ne. nf_noerr) call handle_err(retval)
      retval = nf_def_dim(ncid, "y", NY, y_dimid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Define the variable. 
      dimids(1) = y_dimid
      dimids(2) = x_dimid
      retval = NF_DEF_VAR(ncid, "data", NF_INT, NDIMS, dimids, varid)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Turn on chunking.
      chunks(1) = NY
      chunks(2) = NX
      retval = NF_DEF_VAR_chunking(ncid, varid, 0, chunks)
      if (retval .ne. nf_noerr) call handle_err(retval)

C     Set variable to big-endian (default is whatever is native to
C     writing machine).
      retval = NF_DEF_VAR_endian(ncid, varid, NF_ENDIAN_BIG)
      if (retval .ne. nf_noerr) call handle_err(retval)
@end example

@node NF_INQ_VAR_ENDIAN, NF_INQ_VARID, NF_DEF_VAR_ENDIAN, Variables
@section Learn About Endian Parameters for a Variable: @code{NF_INQ_VAR_ENDIAN}
@findex NF_INQ_VAR_ENDIAN

The function NF_INQ_VAR_ENDIAN returns the endianness settings for a
variable in a netCDF-4 file.

@heading Usage 

@example
NF_INQ_VAR_ENDIAN(INTEGER NCID, INTEGER VARID, INTEGER ENDIAN)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.

@item ENDIAN
NF_INQ_VAR_ENDIAN will set this to NF_ENDIAN_LITTLE if this variable
is stored in little-endian format, NF_ENDIAN_BIG if it is stored in
big-endian format, and NF_ENDIAN_NATIVE if the endianness is not set,
and the variable is not created yet.

@end table

@heading Errors 

NF_INQ_VAR_ENDIAN returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. 

Possible return codes include:

@table @code

@item NF_NOERR
No error.

@item NF_BADID
Bad ncid.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_ENOTVAR
Can't find this variable.

@end table

@heading Example

In this example from nf_test/ftst_vars.F, the endianness of a variable
is checked to make sure it is NF_ENDIAN_BIG.

@example
      retval = nf_inq_var_endian(ncid, varid, endianness)
      if (retval .ne. nf_noerr) call handle_err(retval)
      if (endianness .ne. NF_ENDIAN_BIG) stop 2
@end example

@node NF_INQ_VARID, NF_INQ_VAR family, NF_INQ_VAR_ENDIAN, Variables
@section Get a Variable ID from Its Name: NF_INQ_VARID 
@findex NF_INQ_VARID 

The function NF_INQ_VARID returns the ID of a netCDF variable, given
its name.

@heading Usage
@example
INTEGER FUNCTION NF_INQ_VARID(INTEGER NCID, CHARACTER*(*) NAME, 
                              INTEGER varid)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item NAME
Variable name for which ID is desired.
 
@item varid
Returned variable ID.
@end table

@heading Errors 

NF_INQ_VARID returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The specified variable name is not a valid name for a variable in the
specified netCDF dataset.

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_INQ_VARID to find out the ID of a variable
named rh in an existing netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER  STATUS, NCID, RHID
   ... 
STATUS = NF_OPEN ('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example


@node NF_INQ_VAR family, NF_PUT_VAR1_  type, NF_INQ_VARID, Variables
@section Get Information about a Variable from Its ID: NF_INQ_VAR family
@findex NF_INQ_VAR family

A family of functions that returns information about a netCDF
variable, given its ID. Information about a variable includes its
name, type, number of dimensions, a list of dimension IDs describing
the shape of the variable, and the number of variable attributes that
have been assigned to the variable.

The function NF_INQ_VAR returns all the information about a netCDF
variable, given its ID. The other functions each return just one item
of information about a variable.

These other functions include NF_INQ_VARNAME, NF_INQ_VARTYPE,
NF_INQ_VARNDIMS, NF_INQ_VARDIMID, and NF_INQ_VARNATTS.

@heading Usage 
@example
INTEGER FUNCTION NF_INQ_VAR      (INTEGER NCID, INTEGER VARID,
                                  CHARACTER*(*) name, INTEGER xtype,
                                  INTEGER ndims, INTEGER dimids(*),
                                  INTEGER natts)
INTEGER FUNCTION NF_INQ_VARNAME  (INTEGER NCID, INTEGER VARID, 
                                  CHARACTER*(*) name)
INTEGER FUNCTION NF_INQ_VARTYPE  (INTEGER NCID, INTEGER VARID, 
                                  INTEGER xtype)
INTEGER FUNCTION NF_INQ_VARNDIMS (INTEGER NCID, INTEGER VARID, 
                                  INTEGER ndims)
INTEGER FUNCTION NF_INQ_VARDIMID (INTEGER NCID, INTEGER VARID, 
                                  INTEGER dimids(*))
INTEGER FUNCTION NF_INQ_VARNATTS (INTEGER NCID, INTEGER VARID, 
                                  INTEGER natts)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item NAME
Returned variable name. The caller must allocate space for the
returned name. The maximum possible length, in characters, of a
variable name is given by the predefined constant NF_MAX_NAME.
 
@item xtype
Returned variable type, one of the set of predefined netCDF external
data types. The type of this parameter, NF_TYPE, is defined in the
netCDF header file. The valid netCDF external data types are NF_BYTE,
NF_CHAR, NF_SHORT, NF_INT, NF_FLOAT, AND NF_DOUBLE.
 
@item ndims
Returned number of dimensions the variable was defined as using. For
example, 2 indicates a matrix, 1 indicates a vector, and 0 means the
variable is a scalar with no dimensions.
 
@item dimids
Returned vector of *ndimsp dimension IDs corresponding to the
variable dimensions. The caller must allocate enough space for a
vector of at least *ndimsp integers to be returned. The maximum
possible number of dimensions for a variable is given by the
predefined constant NF_MAX_VAR_DIMS.
 
@item natts
Returned number of variable attributes assigned to this variable.

@end table

These functions return the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@end itemize

@heading Example 

Here is an example using NF_INQ_VAR to find out about a variable named
rh in an existing netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER  STATUS, NCID
INTEGER  RHID               ! variable ID
CHARACTER*31 RHNAME         ! variable name
INTEGER  RHTYPE             ! variable type
INTEGER  RHN                ! number of dimensions
INTEGER  RHDIMS(NF_MAX_VAR_DIMS)   ! variable shape
INTEGER  RHNATT                    ! number of attributes
   ... 
STATUS = NF_OPEN ('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)  ! get ID
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_INQ_VAR (NCID, RHID, RHNAME, RHTYPE, RHN, RHDIMS, RHNATT)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_PUT_VAR1_  type, NF_PUT_VAR_ type, NF_INQ_VAR family, Variables
@section Write a Single Data Value: NF_PUT_VAR1_  type 
@findex NF_PUT_VAR1_  type 

The functions NF_PUT_VAR1_type (for various types) put a single data
value of the specified type into a variable of an open netCDF dataset
that is in data mode. Inputs are the netCDF ID, the variable ID, an
index that specifies which value to add or alter, and the data
value. The value is converted to the external data type of the
variable, if necessary.

@heading Usage 
@example
INTEGER FUNCTION  NF_PUT_VAR1_TEXT(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), CHARACTER CHVAL)
INTEGER FUNCTION  NF_PUT_VAR1_INT1(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), INTEGER*1 I1VAL)
INTEGER FUNCTION  NF_PUT_VAR1_INT2(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), INTEGER*2 I2VAL)
INTEGER FUNCTION  NF_PUT_VAR1_INT (INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), INTEGER   IVAL)
INTEGER FUNCTION  NF_PUT_VAR1_REAL(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), REAL      RVAL)
INTEGER FUNCTION  NF_PUT_VAR1_DOUBLE(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), DOUBLE    DVAL) 
INTEGER FUNCTION  NF_PUT_VAR1(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), *) 
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item INDEX
The index of the data value to be written. The indices are relative
to 1, so for example, the first data value of a two-dimensional
variable would have index (1,1). The elements of index must correspond
to the variable's dimensions. Hence, if the variable uses the
unlimited dimension, the last index would correspond to the record number.
 
@item CHVAL
@itemx I1VAL
@itemx I2VAL
@itemx IVAL
@itemx RVAL
@itemx DVAL
Pointer to the data value to be written. If the type of data values
differs from the netCDF variable type, type conversion will
occur. @xref{Type Conversion,,, netcdf, @value{n-man}}.
@end table

@heading Errors 

NF_PUT_VAR1_  type returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset.

@item
The specified indices were out of range for the rank of the specified
variable. For example, a negative index or an index that is larger
than the corresponding dimension length will cause an error.

@item
The specified value is out of the range of values representable by the
external data type of the variable.

@item
The specified netCDF is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_PUT_VAR1_DOUBLE to set the (4,3,2) element
of the variable named rh to 0.5 in an existing netCDF dataset named
foo.nc. For simplicity in this example, we assume that we know that rh
is dimensioned with lon, lat, and time, so we want to set the value of
rh that corresponds to the fourth lon value, the third lat value, and
the second time value:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER  STATUS             ! error status
INTEGER  NCID
INTEGER  RHID               ! variable ID
INTEGER  RHINDX(3)          ! where to put value
DATA RHINDX /4, 3, 2/
   ... 
STATUS = NF_OPEN ('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)  ! get ID
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_PUT_VAR1_DOUBLE (NCID, RHID, RHINDX, 0.5)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_PUT_VAR_ type, NF_PUT_VARA_ type, NF_PUT_VAR1_  type, Variables
@section Write an Entire Variable: NF_PUT_VAR_ @var{type} 
@findex NF_PUT_VAR_ type 

The NF_PUT_VAR_ @var{type} family of functions write all the values of a
variable into a netCDF variable of an open netCDF dataset. This is the
simplest interface to use for writing a value in a scalar variable or
whenever all the values of a multidimensional variable can all be
written at once. The values to be written are associated with the
netCDF variable by assuming that the last dimension of the netCDF
variable varies fastest in the C interface. The values are converted
to the external data type of the variable, if necessary.

Take care when using the simplest forms of this interface with record
variables (variables that use the NF_UNLIMITED dimension) when you
don't specify how many records are to be written.  If you try to write
all the values of a record variable into a netCDF file that has no
record data yet (hence has 0 records), nothing will be written.
Similarly, if you try to write all the values of a record variable
from an array but there are more records in the file than you assume,
more in-memory data will be accessed than you expect, which may cause
a segmentation violation.  To avoid such problems, it is better to use
the NF_PUT_VARA_type interfaces for variables that use the
NF_UNLIMITED dimension.  @xref{NF_PUT_VARA_ type}.

@heading Usage 
@example
INTEGER FUNCTION NF_PUT_VAR_TEXT  (INTEGER NCID, INTEGER VARID,
                                   CHARACTER*(*) TEXT)
INTEGER FUNCTION NF_PUT_VAR_INT1  (INTEGER NCID, INTEGER VARID,
                                   INTEGER*1 I1VALS(*))
INTEGER FUNCTION NF_PUT_VAR_INT2  (INTEGER NCID, INTEGER VARID,
                                   INTEGER*2 I2VALS(*))
INTEGER FUNCTION NF_PUT_VAR_INT   (INTEGER NCID, INTEGER VARID,
                                   INTEGER IVALS(*))
INTEGER FUNCTION NF_PUT_VAR_REAL  (INTEGER NCID, INTEGER VARID,
                                   REAL RVALS(*))
INTEGER FUNCTION NF_PUT_VAR_DOUBLE(INTEGER NCID, INTEGER VARID,
                                   DOUBLE DVALS(*))
INTEGER FUNCTION NF_PUT_VAR       (INTEGER NCID, INTEGER VARID,
                                   VALS(*))
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item TEXT
@itemx I1VALS
@itemx I2VALS
@itemx IVALS
@itemx RVALS
@itemx DVALS
@itemx VALS
The block of data values to be written. The data should be of the type
appropriate for the function called. You cannot put CHARACTER data
into a numeric variable or numeric data into a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur (@pxref{Type Conversion,,, netcdf,
@value{n-man}}). The order in which the data will be written
into the specified variable is with the first dimension varying
fastest (like the ordinary FORTRAN convention).
@end table

@heading Errors 

Members of the NF_PUT_VAR_ @var{type} family return the value NF_NOERR if no
errors occurred. Otherwise, the returned status indicates an
error. Possible causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
One or more of the specified values are out of the range of values
representable by the external data type of the variable.

@item
One or more of the specified values are out of the range of values
representable by the external data type of the variable.

@item
The specified netCDF dataset is in define mode rather than data mode.

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_PUT_VAR_DOUBLE to add or change all the
values of the variable named rh to 0.5 in an existing netCDF dataset
named foo.nc. For simplicity in this example, we assume that we know
that rh is dimensioned with lon and lat, and that there are ten
lon values and five lat values.

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (LATS=5, LONS=10) ! dimension lengths
INTEGER  STATUS, NCID
INTEGER  RHID                        ! variable ID
DOUBLE RHVALS(LONS, LATS)
   ... 
STATUS = NF_OPEN ('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
DO 10 ILON = 1, LONS
   DO 10 ILAT = 1, LATS
         RHVALS(ILON, ILAT) = 0.5
10 CONTINUE
STATUS = NF_PUT_var_DOUBLE (NCID, RHID, RHVALS)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_PUT_VARA_ type, NF_PUT_VARS_ type, NF_PUT_VAR_ type, Variables
@section Write an Array of Values: NF_PUT_VARA_ @var{type} 
@findex NF_PUT_VARA_ type 

The function NF_PUT_VARA_ @var{type} writes values into a netCDF variable of
an open netCDF dataset. The part of the netCDF variable to write is
specified by giving a corner and a vector of edge lengths that refer
to an array section of the netCDF variable. The values to be written
are associated with the netCDF variable by assuming that the first
dimension of the netCDF variable varies fastest in the FORTRAN
interface. The netCDF dataset must be in data mode.

@heading Usage 
@example
INTEGER FUNCTION NF_PUT_VARA_TEXT(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  CHARACTER*(*) TEXT)
INTEGER FUNCTION NF_PUT_VARA_INT1(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  INTEGER*1 I1VALS(*))
INTEGER FUNCTION NF_PUT_VARA_INT2(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  INTEGER*2 I2VALS(*))
INTEGER FUNCTION NF_PUT_VARA_INT (INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  INTEGER IVALS(*))
INTEGER FUNCTION NF_PUT_VARA_REAL(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  REAL RVALS(*))
INTEGER FUNCTION NF_PUT_VARA_DOUBLE(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  DOUBLE DVALS(*)) 
INTEGER FUNCTION NF_PUT_VARA     (INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  VALS(*)) 
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item START
A vector of integers specifying the index in the variable where the
first of the data values will be written. The indices are relative to
1, so for example, the first data value of a variable would have index
(1, 1, ..., 1). The length of START must be the same as the number of
dimensions of the specified variable. The elements of START must
correspond to the variable's dimensions in order. Hence, if the
variable is a record variable, the last index would correspond to the
starting record number for writing the data values.
 
@item COUNT
A vector of integers specifying the edge lengths along each dimension
of the block of data values to written. To write a single value, for
example, specify COUNT as (1, 1, ..., 1). The length of COUNT is the
number of dimensions of the specified variable. The elements of COUNT
correspond to the variable's dimensions. Hence, if the variable is a
record variable, the last element of COUNT corresponds to a count of
the number of records to write.

Note: setting any element of the count array to zero causes the
function to exit without error, and without doing anything.
 
@item TEXT
@itemx I1VALS
@itemx I2VALS
@itemx IVALS
@itemx RVALS
@itemx DVALS
@itemx VALS
The block of data values to be written. The data should be of the type
appropriate for the function called. You cannot put CHARACTER data
into a numeric variable or numeric data into a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur (@pxref{Type Conversion,,, netcdf,
@value{n-man}}).
@end table

@heading Errors 

NF_PUT_VARA_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified corner indices were out of range for the rank of the
specified variable. For example, a negative index, or an index that is
larger than the corresponding dimension length will cause an error.

@item
The specified edge lengths added to the specified corner would have
referenced data out of range for the rank of the specified
variable. For example, an edge length that is larger than the
corresponding dimension length minus the corner index will cause an
error.

@item
One or more of the specified values are out of the range of values
representable by the external data type of the variable.

@item
The specified netCDF dataset is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_PUT_VARA_DOUBLE to add or change all the
values of the variable named rh to 0.5 in an existing netCDF dataset
named foo.nc. For simplicity in this example, we assume that we know
that rh is dimensioned with time, lat, and lon, and that there are
three time values, five lat values, and ten lon values.

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (NDIMS=3)         ! number of dimensions
PARAMETER (TIMES=3, LATS=5, LONS=10) ! dimension lengths
INTEGER  STATUS, NCID, TIMES
INTEGER  RHID               ! variable ID
INTEGER  START(NDIMS), COUNT(NDIMS)
DOUBLE RHVALS(LONS, LATS, TIMES)
DATA START /1, 1, 1/        ! start at first value
DATA COUNT /LONS, LATS, TIMES/
   ... 
STATUS = NF_OPEN ('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
DO 10 ILON = 1, LONS
   DO 10 ILAT = 1, LATS
      DO 10 ITIME = 1, TIMES
         RHVALS(ILON, ILAT, ITIME) = 0.5
10 CONTINUE
STATUS = NF_PUT_VARA_DOUBLE (NCID, RHID, START, COUNT, RHVALS)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_PUT_VARS_ type, NF_PUT_VARM_ type, NF_PUT_VARA_ type, Variables
@section NF_PUT_VARS_ @var{type} 
@findex NF_PUT_VARS_ type 

Each member of the family of functions NF_PUT_VARS_ @var{type} writes a
subsampled (strided) array section of values into a netCDF variable of
an open netCDF dataset. The subsampled array section is specified by
giving a corner, a vector of counts, and a stride vector. The netCDF
dataset must be in data mode.

@heading Usage 
@example
INTEGER FUNCTION NF_PUT_VARS_TEXT  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*),CHARACTER*(*) TEXT)
INTEGER FUNCTION NF_PUT_VARS_INT1  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*),INTEGER*1 I1VALS(*))
INTEGER FUNCTION NF_PUT_VARS_INT2  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*),INTEGER*2 I2VALS(*))
INTEGER FUNCTION NF_PUT_VARS_INT   (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IVALS(*))
INTEGER FUNCTION NF_PUT_VARS_REAL  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*),  REAL RVALS(*))
INTEGER FUNCTION NF_PUT_VARS_DOUBLE(INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*),  DOUBLE DVALS(*))
INTEGER FUNCTION NF_PUT_VARS       (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), VALS(*))
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item START
A vector of integers specifying the index in the variable where the
first of the data values will be written. The indices are relative to
1, so for example, the first data value of a variable would have index
(1, 1, ..., 1). The elements of START correspond, in order, to the
variable's dimensions. Hence, if the variable is a record variable,
the last index would correspond to the starting record number for
writing the data values.
 
@item COUNT
A vector of integers specifying the number of indices selected along
each dimension. To write a single value, for example, specify COUNT as
(1, 1, ..., 1). The elements of COUNT correspond, in order, to the
variable's dimensions. Hence, if the variable is a record variable,
the last element of COUNT corresponds to a count of the number of
records to write.

Note: setting any element of the count array to zero causes the
function to exit without error, and without doing anything.
 
@item STRIDE
A vector of integers that specifies the sampling interval along each
dimension of the netCDF variable. The elements of the stride vector
correspond, in order, to the netCDF variable's dimensions (STRIDE(1)
gives the sampling interval along the most rapidly varying dimension
of the netCDF variable). Sampling intervals are specified in
type-independent units of elements (a value of 1 selects consecutive
elements of the netCDF variable along the corresponding dimension, a
value of 2 selects every other element, etc.).
 
@item TEXT
@itemx I1VALS
@itemx I2VALS
@itemx IVALS
@itemx RVALS
@itemx DVALS
@itemx VALS
The block of data values to be written. The data should be of the type
appropriate for the function called. You cannot put CHARACTER data
into a numeric variable or numeric data into a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur (@pxref{Type Conversion,,, netcdf,
@value{n-man}}).
@end table

@heading Errors 

NF_PUT_VARS_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:
@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified start, count and stride generate an index which is out
of range.

@item
One or more of the specified values are out of the range of values
representable by the external data type of the variable.

@item
The specified netCDF is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@end itemize

@heading Example 

Here is an example of using NF_PUT_VARS_REAL to write -- from an
internal array -- every other point of a netCDF variable named rh
which is described by the FORTRAN declaration REAL RH(6,4) (note the
size of the dimensions):

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (NDIM=2)   ! rank of netCDF variable
INTEGER NCID         ! netCDF dataset ID
INTEGER STATUS       ! return code
INTEGER RHID         ! variable ID
INTEGER START(NDIM)  ! netCDF variable start point
INTEGER COUNT(NDIM)  ! size of internal array
INTEGER STRIDE(NDIM) ! netCDF variable subsampling intervals
REAL RH(3,2)         ! note subsampled sizes for netCDF variable
                     ! dimensions
DATA START   /1, 1/  ! start at first netCDF variable value
DATA COUNT   /3, 2/  ! size of internal array: entire (subsampled)
                     ! netCDF variable
DATA STRIDE /2, 2/   ! access every other netCDF element
   ... 
STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID(NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_PUT_VARS_REAL(NCID, RHID, START, COUNT, STRIDE, RH)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)


@end example

@node NF_PUT_VARM_ type, NF_GET_VAR1_ type, NF_PUT_VARS_ type, Variables
@section NF_PUT_VARM_ @var{type} 
@findex NF_PUT_VARM_ type 

The NF_PUT_VARM_ @var{type} family of functions writes a mapped array
section of values into a netCDF variable of an open netCDF
dataset. The mapped array section is specified by giving a corner, a
vector of counts, a stride vector, and an index mapping vector. The
index mapping vector is a vector of integers that specifies the
mapping between the dimensions of a netCDF variable and the in-memory
structure of the internal data array. No assumptions are made about
the ordering or length of the dimensions of the data array. The netCDF
dataset must be in data mode.

@heading Usage 
@example
INTEGER FUNCTION NF_PUT_VARM_TEXT  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            CHARACTER*(*) TEXT)
INTEGER FUNCTION NF_PUT_VARM_INT1  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            INTEGER*1 I1VALS(*))
INTEGER FUNCTION NF_PUT_VARM_INT2  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            INTEGER*2 I2VALS(*))
INTEGER FUNCTION NF_PUT_VARM_INT   (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            INTEGER IVALS(*))
INTEGER FUNCTION NF_PUT_VARM_REAL  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            REAL RVALS(*))
INTEGER FUNCTION NF_PUT_VARM_DOUBLE(INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            DOUBLE DVALS(*))
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item START
A vector of integers specifying the index in the variable where the
first of the data values will be written. The indices are relative to
1, so for example, the first data value of a variable would have index
(1, 1, ..., 1). The elements of START correspond, in order, to the
variable's dimensions. Hence, if the variable is a record variable,
the last index would correspond to the starting record number for
writing the data values.
 
@item COUNT
A vector of integers specifying the number of indices selected along
each dimension. To write a single value, for example, specify COUNT as
(1, 1, ..., 1). The elements of COUNT correspond, in order, to the
variable's dimensions. Hence, if the variable is a record variable,
the last element of COUNT corresponds to a count of the number of
records to write.

Note: setting any element of the count array to zero causes the
function to exit without error, and without doing anything.
 
@item STRIDE
A vector of integers that specifies the sampling interval along each
dimension of the netCDF variable. The elements of the stride vector
correspond, in order, to the netCDF variable's dimensions (STRIDE(1)
gives the sampling interval along the most rapidly varying dimension
of the netCDF variable). Sampling intervals are specified in
type-independent units of elements (a value of 1 selects consecutive
elements of the netCDF variable along the corresponding dimension, a
value of 2 selects every other element, etc.).

@item IMAP
A vector of integers that specifies the mapping between the dimensions
of a netCDF variable and the in-memory structure of the internal data
array. The elements of the index mapping vector correspond, in order,
to the netCDF variable's dimensions (IMAP(1) gives the distance
between elements of the internal array corresponding to the most
rapidly varying dimension of the netCDF variable). Distances between
elements are specified in units of elements (the distance between
internal elements that occupy adjacent memory locations is 1 and not
the element's byte-length as in netCDF 2).

@item TEXT
@itemx I1VALS
@itemx I2VALS
@itemx IVALS
@itemx RVALS
@itemx DVALS
The data values to be written. The data should be of the type
appropriate for the function called. You cannot put CHARACTER data
into a numeric variable or numeric data into a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur (@pxref{Type Conversion,,, netcdf,
@value{n-man}}).

@end table
 
@heading Errors 

NF_PUT_VARM_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified START, COUNT, and STRIDE generate an index which is out
of range. Note that no error checking is possible on the imap vector.

@item
One or more of the specified values are out of the range of values
representable by the external data type of the variable.

@item
The specified netCDF is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@end itemize

@heading Example 

The following IMAP vector maps in the trivial way a 2x3x4 netCDF
variable and an internal array of the same shape:

@example
REAL A(2,3,4)       ! same shape as netCDF variable
INTEGER IMAP(3)
DATA IMAP /1, 2, 6/ ! netCDF dimension       inter-element distance
                    ! ----------------       ----------------------
                    ! most rapidly varying       1
                    ! intermediate               2 (=IMAP(1)*2)
                    ! most slowly varying        6 (=IMAP(2)*3)
@end example

Using the IMAP vector above with NF_PUT_VARM_REAL obtains the same
result as simply using NF_PUT_VAR_REAL.

Here is an example of using NF_PUT_VARM_REAL to write -- from a
transposed, internal array -- a netCDF variable named rh which is
described by the FORTRAN declaration REAL RH(4,6) (note the size and
order of the dimensions):

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (NDIM=2)   ! rank of netCDF variable
INTEGER NCID         ! netCDF ID
INTEGER STATUS       ! return code
INTEGER RHID         ! variable ID
INTEGER START(NDIM)  ! netCDF variable start point
INTEGER COUNT(NDIM)  ! size of internal array
INTEGER STRIDE(NDIM) ! netCDF variable subsampling intervals
INTEGER IMAP(NDIM)   ! internal array inter-element distances
REAL RH(6,4)         ! note transposition of netCDF variable dimensions
DATA START   /1, 1/  ! start at first netCDF variable element
DATA COUNT   /4, 6/  ! entire netCDF variable; order corresponds
                     ! to netCDF variable -- not internal array
DATA STRIDE /1, 1/   ! sample every netCDF element
DATA IMAP   /6, 1/   ! would be /1, 4/ if not transposing

STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID(NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_PUT_VARM_REAL(NCID, RHID, START, COUNT, STRIDE, IMAP, RH)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

Here is another example of using NF_PUT_VARM_REAL to write -- from a
transposed, internal array -- a subsample of the same netCDF variable,
by writing every other point of the netCDF variable:

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (NDIM=2)   ! rank of netCDF variable
INTEGER NCID         ! netCDF dataset ID
INTEGER STATUS       ! return code
INTEGER RHID         ! variable ID
INTEGER START(NDIM)  ! netCDF variable start point
INTEGER COUNT(NDIM)  ! size of internal array
INTEGER STRIDE(NDIM) ! netCDF variable subsampling intervals
INTEGER IMAP(NDIM)   ! internal array inter-element distances
REAL RH(3,2)         ! note transposition of (subsampled) dimensions
DATA START   /1, 1/  ! start at first netCDF variable value
DATA COUNT   /2, 3/  ! order of (subsampled) dimensions corresponds
                     ! to netCDF variable -- not internal array
DATA STRIDE /2, 2/   ! sample every other netCDF element
DATA IMAP   /3, 1/   ! would be `1, 2' if not transposing
   ... 
STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID(NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_PUT_VARM_REAL(NCID, RHID, START, COUNT, STRIDE, IMAP, RH)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_GET_VAR1_ type, NF_GET_VAR_ type, NF_PUT_VARM_ type, Variables
@section NF_GET_VAR1_ @var{type} 
@findex NF_GET_VAR1_ type 

The functions NF_GET_VAR1_ @var{type} get a single data value from a
variable of an open netCDF dataset that is in data mode. Inputs are
the netCDF ID, the variable ID, a multidimensional index that
specifies which value to get, and the address of a location into which
the data value will be read. The value is converted from the external
data type of the variable, if necessary.

@heading Usage 
@example
INTEGER FUNCTION  NF_GET_VAR1_TEXT(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), CHARACTER CHVAL)
INTEGER FUNCTION  NF_GET_VAR1_INT1(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), INTEGER*1 I1VAL)
INTEGER FUNCTION  NF_GET_VAR1_INT2(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), INTEGER*2 I2VAL)
INTEGER FUNCTION  NF_GET_VAR1_INT (INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), INTEGER   IVAL)
INTEGER FUNCTION  NF_GET_VAR1_REAL(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), REAL      RVAL)
INTEGER FUNCTION  NF_GET_VAR1_DOUBLE(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), DOUBLE    DVAL) 
INTEGER FUNCTION  NF_GET_VAR1(INTEGER NCID, INTEGER VARID,
                                   INTEGER INDEX(*), VAL) 
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item INDEX
The index of the data value to be read. The indices are relative to 1,
so for example, the first data value of a two-dimensional variable has
index (1,1). The elements of index correspond to the variable's
dimensions. Hence, if the variable is a record variable, the last
index is the record number.
 
@item CHVAL
@itemx I1VAL
@itemx I2VAL
@itemx IVAL
@itemx RVAL
@itemx DVAL
@itemx VAL
The location into which the data value will be read. You cannot get
CHARACTER data from a numeric variable or numeric data from a
character variable. For numeric data, if the type of data differs from
the netCDF variable type, type conversion will occur. (@pxref{Type
Conversion,,, netcdf, @value{n-man}}).
@end table

@heading Errors 

NF_GET_VAR1_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified indices were out of range for the rank of the specified
variable. For example, a negative index or an index that is larger
than the corresponding dimension length will cause an error.

@item
The value is out of the range of values representable by the desired
data type.

@item
The specified netCDF is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_GET_VAR1_DOUBLE to get the (4,3,2) element
of the variable named rh in an existing netCDF dataset named
foo.nc. For simplicity in this example, we assume that we know that rh
is dimensioned with lon, lat, and time, so we want to get the value of
rh that corresponds to the fourth lon value, the third lat value, and
the second time value:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID
INTEGER RHID           ! variable ID
INTEGER RHINDX(3)      ! where to get value
DOUBLE PRECISION RHVAL ! put it here
DATA RHINDX /4, 3, 2/
   ... 
STATUS = NF_OPEN ('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_GET_VAR1_DOUBLE (NCID, RHID, RHINDX, RHVAL)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_GET_VAR_ type, NF_GET_VARA_ type, NF_GET_VAR1_ type, Variables
@section NF_GET_VAR_ @var{type} 
@findex NF_GET_VAR_ type 

The members of the NF_GET_VAR_ @var{type} family of functions read all the
values from a netCDF variable of an open netCDF dataset. This is the
simplest interface to use for reading the value of a scalar variable
or when all the values of a multidimensional variable can be read at
once. The values are read into consecutive locations with the first
dimension varying fastest. The netCDF dataset must be in data mode.

Take care when using the simplest forms of this interface with record
variables (variables that use the NF_UNLIMITED dimension) when you
don't specify how many records are to be read. If you try to read all
the values of a record variable into an array but there are more
records in the file than you assume, more data will be read than you
expect, which may cause a segmentation violation.  To avoid such
problems, it is better to use the NF_GET_VARA_type interfaces for
variables that use the NF_UNLIMITED dimension.  @xref{NF_GET_VARA_
type}.

@heading Usage 
@example
INTEGER FUNCTION NF_GET_VAR_TEXT  (INTEGER NCID, INTEGER VARID,
                                   CHARACTER*(*) text)
INTEGER FUNCTION NF_GET_VAR_INT1  (INTEGER NCID, INTEGER VARID,
                                   INTEGER*1 i1vals(*))
INTEGER FUNCTION NF_GET_VAR_INT2  (INTEGER NCID, INTEGER VARID,
                                   INTEGER*2 i2vals(*))
INTEGER FUNCTION NF_GET_VAR_INT   (INTEGER NCID, INTEGER VARID,
                                   INTEGER ivals(*))
INTEGER FUNCTION NF_GET_VAR_REAL  (INTEGER NCID, INTEGER VARID,
                                   REAL rvals(*))
INTEGER FUNCTION NF_GET_VAR_DOUBLE(INTEGER NCID, INTEGER VARID,
                                   DOUBLE dvals(*))
INTEGER FUNCTION NF_GET_VAR       (INTEGER NCID, INTEGER VARID,
                                   vals(*))
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item TEXT
@itemx I1VALS
@itemx I2VALS
@itemx IVALS
@itemx RVALS
@itemx DVALS
@itemx VALS
The block of data values to be read. The data should be of the type
appropriate for the function called. You cannot read CHARACTER data
from a numeric variable or numeric data from a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur (@pxref{Type Conversion,,, netcdf,
@value{n-man}}).
@end table

@heading Errors 

NF_GET_VAR_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
One or more of the values are out of the range of values representable
by the desired type.

@item
The specified netCDF is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_GET_VAR_DOUBLE to read all the values of
the variable named rh from an existing netCDF dataset named
foo.nc. For simplicity in this example, we assume that we know that rh
is dimensioned with lon and lat, and that there are ten lon
values and five lat values.

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (LATS=5, LONS=10) ! dimension lengths
INTEGER STATUS, NCID
INTEGER RHID                         ! variable ID
DOUBLE RHVALS(LONS, LATS)
   ... 
STATUS = NF_OPEN ('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_GET_VAR_DOUBLE (NCID, RHID, RHVALS)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_GET_VARA_ type, NF_GET_VARS_ type, NF_GET_VAR_ type, Variables
@section NF_GET_VARA_ @var{type} 
@findex NF_GET_VARA_ type 

The members of the NF_GET_VARA_ @var{type} family of functions read an array
of values from a netCDF variable of an open netCDF dataset. The array
is specified by giving a corner and a vector of edge lengths. The
values are read into consecutive locations with the first dimension
varying fastest. The netCDF dataset must be in data mode.

@heading Usage 
@example
INTEGER FUNCTION NF_GET_VARA_TEXT(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  CHARACTER*(*) text)
INTEGER FUNCTION NF_GET_VARA_INT1(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  INTEGER*1 i1vals(*))
INTEGER FUNCTION NF_GET_VARA_INT2(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  INTEGER*2 i2vals(*))
INTEGER FUNCTION NF_GET_VARA_INT (INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  INTEGER ivals(*))
INTEGER FUNCTION NF_GET_VARA_REAL(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  REAL rvals(*))
INTEGER FUNCTION NF_GET_VARA_DOUBLE(INTEGER NCID, INTEGER VARID,
                                  INTEGER START(*), INTEGER COUNT(*),
                                  DOUBLE dvals(*))
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item START
A vector of integers specifying the index in the variable where the
first of the data values will be read. The indices are relative to 1,
so for example, the first data value of a variable would have index
(1, 1, ..., 1). The length of START must be the same as the number of
dimensions of the specified variable. The elements of START
correspond, in order, to the variable's dimensions. Hence, if the
variable is a record variable, the last index would correspond to the
starting record number for reading the data values.

@item COUNT
A vector of integers specifying the edge lengths along each dimension
of the block of data values to be read. To read a single value, for
example, specify COUNT as (1, 1, ..., 1). The length of COUNT is the
number of dimensions of the specified variable. The elements of COUNT
correspond, in order, to the variable's dimensions. Hence, if the
variable is a record variable, the last element of COUNT corresponds
to a count of the number of records to read.

Note: setting any element of the count array to zero causes the
function to exit without error, and without doing anything.
 
@item text
@itemx i1vals
@itemx i2vals
@itemx ivals
@itemx rvals
@itemx dvals
The block of data values to be read. The data should be of the type
appropriate for the function called. You cannot read CHARACTER data
from a numeric variable or numeric data from a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur (@pxref{Type Conversion,,, netcdf,
@value{n-man}}).
@end table
 
@heading Errors 

NF_GET_VARA_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified corner indices were out of range for the rank of the
specified variable. For example, a negative index or an index that is
larger than the corresponding dimension length will cause an error.

@item
The specified edge lengths added to the specified corner would have
referenced data out of range for the rank of the specified
variable. For example, an edge length that is larger than the
corresponding dimension length minus the corner index will cause an
error.

@item
One or more of the values are out of the range of values representable
by the desired type.

@item
The specified netCDF is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_GET_VARA_DOUBLE to read all the values of
the variable named rh from an existing netCDF dataset named
foo.nc. For simplicity in this example, we assume that we know that rh
is dimensioned with lon, lat, and time, and that there are ten lon
values, five lat values, and three time values.

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (NDIMS=3)                  ! number of dimensions
PARAMETER (TIMES=3, LATS=5, LONS=10) ! dimension lengths
INTEGER STATUS, NCID
INTEGER RHID                         ! variable ID
INTEGER START(NDIMS), COUNT(NDIMS)
DOUBLE RHVALS(LONS, LATS, TIMES)
DATA START /1, 1, 1/                 ! start at first value
DATA COUNT /LONS, LATS, TIMES/       ! get all the values
   ... 
STATUS = NF_OPEN ('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_GET_VARA_DOUBLE (NCID, RHID, START, COUNT, RHVALS)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_GET_VARS_ type, NF_GET_VARM_ type, NF_GET_VARA_ type, Variables
@section NF_GET_VARS_ @var{type} 
@findex NF_GET_VARS_ type 

The NF_GET_VARS_ @var{type} family of functions read a subsampled (strided)
array section of values from a netCDF variable of an open netCDF
dataset. The subsampled array section is specified by giving a corner,
a vector of edge lengths, and a stride vector. The values are read
with the first dimension of the netCDF variable varying fastest. The
netCDF dataset must be in data mode.

@heading Usage 
@example
INTEGER FUNCTION NF_GET_VARS_TEXT  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*),CHARACTER*(*) text)
INTEGER FUNCTION NF_GET_VARS_INT1  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*),INTEGER*1 i1vals(*))
INTEGER FUNCTION NF_GET_VARS_INT2  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*),INTEGER*2 i2vals(*))
INTEGER FUNCTION NF_GET_VARS_INT   (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER ivals(*))
INTEGER FUNCTION NF_GET_VARS_REAL  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), REAL rvals(*))
INTEGER FUNCTION NF_GET_VARS_DOUBLE(INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), DOUBLE dvals(*))
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item START
A vector of integers specifying the index in the variable from which
the first of the data values will be read. The indices are relative to
1, so for example, the first data value of a variable would have index
(1, 1, ..., 1). The elements of START correspond, in order, to the
variable's dimensions. Hence, if the variable is a record variable,
the last index would correspond to the starting record number for
reading the data values.

@item COUNT
A vector of integers specifying the number of indices selected along
each dimension. To read a single value, for example, specify COUNT as
(1, 1, ..., 1). The elements of COUNT correspond, in order, to the
variable's dimensions. Hence, if the variable is a record variable,
the last element of COUNT corresponds to a count of the number of
records to read.

Note: setting any element of the count array to zero causes the
function to exit without error, and without doing anything.

@item STRIDE
A vector of integers specifying, for each dimension, the interval
between selected indices or the value 0. The elements of the vector
correspond, in order, to the variable's dimensions. A value of 1
accesses adjacent values of the netCDF variable in the corresponding
dimension; a value of 2 accesses every other value of the netCDF
variable in the corresponding dimension; and so on. A 0 argument is
treated as (1, 1, ..., 1).

@item text
@itemx i1vals
@itemx i2vals
@itemx ivals
@itemx rvals
@itemx dvals
The block of data values to be read. The data should be of the type
appropriate for the function called. You cannot read CHARACTER data
from a numeric variable or numeric data from a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur (@pxref{Type Conversion,,, netcdf,
@value{n-man}}).
@end table

@heading Errors 

NF_GET_VARS_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified start, count and stride generate an index which is out
of range.

@item
One or more of the values are out of the range of values representable
by the desired type.

@item
The specified netCDF is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_GET_VARS_DOUBLE to read every other value
in each dimension of the variable named rh from an existing netCDF
dataset named foo.nc. Values are assigned, using the same dimensional
strides, to a 2-parameter array. For simplicity in this example, we
assume that we know that rh is dimensioned with lon, lat, and time,
and that there are ten lon values, five lat values, and three time
values.

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (NDIMS=3)                  ! number of dimensions
PARAMETER (TIMES=3, LATS=5, LONS=10) ! dimension lengths
INTEGER STATUS, NCID
INTEGER RHID ! variable ID
INTEGER START(NDIMS), COUNT(NDIMS), STRIDE(NDIMS)
DOUBLE DATA(LONS, LATS, TIMES)
DATA START /1, 1, 1/                 ! start at first value
DATA COUNT /LONS, LATS, TIMES/
DATA STRIDE /2, 2, 2/
   ... 
STATUS = NF_OPEN ('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_GET_VARS_DOUBLE(NCID,RHID,START,COUNT,STRIDE,DATA(1,1,1))
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_GET_VARM_ type, Reading and Writing Character String Values, NF_GET_VARS_ type, Variables
@section NF_GET_VARM_ @var{type} 
@findex NF_GET_VARM_ type 

The NF_GET_VARM_ @var{type} family of functions reads a mapped array section
of values from a netCDF variable of an open netCDF dataset. The mapped
array section is specified by giving a corner, a vector of edge
lengths, a stride vector, and an index mapping vector. The index
mapping vector is a vector of integers that specifies the mapping
between the dimensions of a netCDF variable and the in-memory
structure of the internal data array. No assumptions are made about
the ordering or length of the dimensions of the data array. The netCDF
dataset must be in data mode.

@heading Usage 

@example
INTEGER FUNCTION NF_GET_VARM_TEXT  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            CHARACTER*(*) text)
INTEGER FUNCTION NF_GET_VARM_INT1  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            INTEGER*1 i1vals(*))
INTEGER FUNCTION NF_GET_VARM_INT2  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            INTEGER*2 i2vals(*))
INTEGER FUNCTION NF_GET_VARM_INT   (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            INTEGER ivals(*))
INTEGER FUNCTION NF_GET_VARM_REAL  (INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            REAL rvals(*))
INTEGER FUNCTION NF_GET_VARM_DOUBLE(INTEGER NCID, INTEGER VARID,
                            INTEGER START(*), INTEGER COUNT(*),
                            INTEGER STRIDE(*), INTEGER IMAP(*),
                            DOUBLE dvals(*))
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item START
A vector of integers specifying the index in the variable from which
the first of the data values will be read. The indices are relative to
1, so for example, the first data value of a variable would have index
(1, 1, ..., 1). The elements of START correspond, in order, to the
variable's dimensions. Hence, if the variable is a record variable,
the last index would correspond to the starting record number for
reading the data values.

@item COUNT
A vector of integers specifying the number of indices selected along
each dimension. To read a single value, for example, specify COUNT as
(1, 1, ..., 1). The elements of COUNT correspond, in order, to the
variable's dimensions. Hence, if the variable is a record variable,
the last element of COUNT corresponds to a count of the number of
records to read.

Note: setting any element of the count array to zero causes the
function to exit without error, and without doing anything.
 
@item STRIDE
A vector of integers specifying, for each dimension, the interval
between selected indices or the value 0. The elements of the vector
correspond, in order, to the variable's dimensions. A value of 1
accesses adjacent values of the netCDF variable in the corresponding
dimension; a value of 2 accesses every other value of the netCDF
variable in the corresponding dimension; and so on. A 0 argument is
treated as (1, 1, ..., 1).

@item IMAP
A vector of integers that specifies the mapping between the dimensions
of a netCDF variable and the in-memory structure of the internal data
array. IMAP(1) gives the distance between elements of the internal
array corresponding to the most rapidly varying dimension of the
netCDF variable. IMAP(N) (where N is the rank of the netCDF variable)
gives the distance between elements of the internal array
corresponding to the most slowly varying dimension of the netCDF
variable. Intervening IMAP elements correspond to other dimensions of
the netCDF variable in the obvious way. Distances between elements are
specified in units of elements (the distance between internal elements
that occupy adjacent memory locations is 1 and not the element's
byte-length as in netCDF 2).

@item text
@itemx i1vals
@itemx i2vals
@itemx ivals
@itemx rvals
@itemx dvals
The block of data values to be read. The data should be of the type
appropriate for the function called. You cannot read CHARACTER data
from a numeric variable or numeric data from a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur (@pxref{Type Conversion,,, netcdf,
@value{n-man}}).
@end table

@heading Errors 

NF_GET_VARM_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified START, COUNT, and STRIDE generate an index which is out
of range. Note that no error checking is possible on the imap vector.

@item
One or more of the values are out of the range of values representable
by the desired type.

@item
The specified netCDF is in define mode rather than data mode. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@end itemize

@heading Example 

The following IMAP vector maps in the trivial way a 2x3x4 netCDF
variable and an internal array of the same shape:

@example
REAL A(2,3,4)       ! same shape as netCDF variable
INTEGER IMAP(3)
DATA IMAP /1, 2, 6/ ! netCDF dimension       inter-element distance
                    ! ----------------       ----------------------
                    ! most rapidly varying       1
                    ! intermediate               2 (=IMAP(1)*2)
                    ! most slowly varying        6 (=IMAP(2)*3)
@end example

Using the IMAP vector above with NF_GET_VARM_REAL obtains the same
result as simply using NF_GET_VAR_REAL.

Here is an example of using NF_GET_VARM_REAL to transpose a netCDF
variable named rh which is described by the FORTRAN declaration REAL
RH(4,6) (note the size and order of the dimensions):

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (NDIM=2)   ! rank of netCDF variable
INTEGER NCID         ! netCDF dataset ID
INTEGER STATUS       ! return code
INTEGER RHID         ! variable ID
INTEGER START(NDIM)  ! netCDF variable start point
INTEGER COUNT(NDIM)  ! size of internal array
INTEGER STRIDE(NDIM) ! netCDF variable subsampling intervals
INTEGER IMAP(NDIM)   ! internal array inter-element distances
REAL    RH(6,4)      ! note transposition of netCDF variable dimensions
DATA START   /1, 1/  ! start at first netCDF variable element
DATA COUNT   /4, 6/  ! entire netCDF variable; order corresponds
                     ! to netCDF variable -- not internal array
DATA STRIDE /1, 1/   ! sample every netCDF element
DATA IMAP   /6, 1/   ! would be /1, 4/ if not transposing
   ... 
STATUS = NF_OPEN('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID(NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_GET_VARM_REAL(NCID, RHID, START, COUNT, STRIDE, IMAP, RH)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

Here is another example of using NF_GET_VARM_REAL to simultaneously
transpose and subsample the same netCDF variable, by accessing every
other point of the netCDF variable:

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (NDIM=2)   ! rank of netCDF variable
INTEGER NCID         ! netCDF dataset ID
INTEGER STATUS       ! return code
INTEGER RHID         ! variable ID
INTEGER START(NDIM)  ! netCDF variable start point
INTEGER COUNT(NDIM)  ! size of internal array
INTEGER STRIDE(NDIM) ! netCDF variable subsampling intervals
INTEGER IMAP(NDIM)   ! internal array inter-element distances
REAL    RH(3,2)      ! note transposition of (subsampled) dimensions
DATA START   /1, 1/  ! start at first netCDF variable value
DATA COUNT   /2, 3/  ! order of (subsampled) dimensions corresponds
                     ! to netCDF variable -- not internal array
DATA STRIDE /2, 2/   ! sample every other netCDF element
DATA IMAP   /3, 1/   ! would be `1, 2' if not transposing
   ... 
STATUS = NF_OPEN('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID(NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_GET_VARM_REAL(NCID, RHID, START, COUNT, STRIDE, IMAP, RH)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node Reading and Writing Character String Values, Fill Values, NF_GET_VARM_ type, Variables
@section Reading and Writing Character String Values

Character strings are not a primitive netCDF external data type, in
part because FORTRAN does not support the abstraction of
variable-length character strings (the FORTRAN LEN function returns
the static length of a character string, not its dynamic length). As a
result, a character string cannot be written or read as a single
object in the netCDF interface. Instead, a character string must be
treated as an array of characters, and array access must be used to
read and write character strings as variable data in netCDF
datasets. Furthermore, variable-length strings are not supported by
the netCDF interface except by convention; for example, you may treat
a zero byte as terminating a character string, but you must explicitly
specify the length of strings to be read from and written to netCDF
variables.

Character strings as attribute values are easier to use, since the
strings are treated as a single unit for access. However, the value of
a character-string attribute is still an array of characters with an
explicit length that must be specified when the attribute is defined.

When you define a variable that will have character-string values, use
a character-position dimension as the most quickly varying dimension
for the variable (the first dimension for the variable in
FORTRAN). The length of the character-position dimension will be the
maximum string length of any value to be stored in the
character-string variable. Space for maximum-length strings will be
allocated in the disk representation of character-string variables
whether you use the space or not. If two or more variables have the
same maximum length, the same character-position dimension may be used
in defining the variable shapes.

To write a character-string value into a character-string variable,
use either entire variable access or array access. The latter requires
that you specify both a corner and a vector of edge lengths. The
character-position dimension at the corner should be one for
FORTRAN. If the length of the string to be written is n, then the
vector of edge lengths will specify n in the character-position
dimension, and one for all the other dimensions:(n, 1, 1, ..., 1).

In FORTRAN, fixed-length strings may be written to a netCDF dataset
without a terminating character, to save space. Variable-length
strings should follow the C convention of writing strings with a
terminating zero byte so that the intended length of the string can be
determined when it is later read by either C or FORTRAN programs.

The FORTRAN interface for reading and writing strings requires the use
of different functions for accessing string values and numeric values,
because standard FORTRAN does not permit the same formal parameter to
be used for both character values and numeric values. An additional
argument, specifying the declared length of the character string
passed as a value, is required for NF_PUT_VARA_TEXT and
NF_GET_VARA_TEXT. The actual length of the string is specified as the
value of the edge-length vector corresponding to the
character-position dimension.

Here is an example that defines a record variable, tx, for character
strings and stores a character-string value into the third record
using NF_PUT_VARA_TEXT. In this example, we assume the string variable
and data are to be added to an existing netCDF dataset named foo.nc
that already has an unlimited record dimension time.

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER   TDIMS, TXLEN
PARAMETER (TDIMS=2)    ! number of TX dimensions
PARAMETER (TXLEN = 15) ! length of example string
INTEGER  NCID
INTEGER  CHID          ! char position dimension id
INTEGER  TIMEID        ! record dimension id
INTEGER  TXID          ! variable ID
INTEGER  TXDIMS(TDIMS) ! variable shape
INTEGER  TSTART(TDIMS), TCOUNT(TDIMS)
CHARACTER*40 TXVAL     ! max length 40
DATA TXVAL /'example string'/
   ... 
TXVAL(TXLEN:TXLEN) = CHAR(0)   ! null terminate
   ... 
STATUS = NF_OPEN('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_REDEF(NCID)        ! enter define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! define character-position dimension for strings of max length 40
STATUS = NF_DEF_DIM(NCID, "chid", 40, CHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! define a character-string variable
TXDIMS(1) = CHID   ! character-position dimension first
TXDIMS(2) = TIMEID
STATUS = NF_DEF_VAR(NCID, "tx", NF_CHAR, TDIMS, TXDIMS, TXID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_ENDDEF(NCID) ! leave define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! write txval into tx netCDF variable in record 3
TSTART(1) = 1      ! start at beginning of variable
TSTART(2) = 3      ! record number to write
TCOUNT(1) = TXLEN  ! number of chars to write
TCOUNT(2) = 1      ! only write one record
STATUS = NF_PUT_VARA_TEXT (NCID, TXID, TSTART, TCOUNT, TXVAL)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node Fill Values, NF_RENAME_VAR, Reading and Writing Character String Values, Variables
@section Fill Values

What happens when you try to read a value that was never written in an
open netCDF dataset? You might expect that this should always be an
error, and that you should get an error message or an error status
returned. You do get an error if you try to read data from a netCDF
dataset that is not open for reading, if the variable ID is invalid
for the specified netCDF dataset, or if the specified indices are not
properly within the range defined by the dimension lengths of the
specified variable. Otherwise, reading a value that was not written
returns a special fill value used to fill in any undefined values when
a netCDF variable is first written.

You may ignore fill values and use the entire range of a netCDF
external data type, but in this case you should make sure you write
all data values before reading them. If you know you will be writing
all the data before reading it, you can specify that no prefilling of
variables with fill values will occur by calling NF_SET_FILL before
writing. This may provide a significant performance gain for netCDF
writes.

The variable attribute _FillValue may be used to specify the fill
value for a variable. Their are default fill values for each type,
defined in the include file netcdf.inc: NF_FILL_CHAR, NF_FILL_INT1
(same as NF_FILL_BYTE), NF_FILL_INT2 (same as NF_FILL_SHORT),
NF_FILL_INT, NF_FILL_REAL (same as NF_FILL_FLOAT), and NF_FILL_DOUBLE.

The netCDF byte and character types have different default fill
values. The default fill value for characters is the zero byte, a
useful value for detecting the end of variable-length C character
strings. If you need a fill value for a byte variable, it is
recommended that you explicitly define an appropriate _FillValue
attribute, as generic utilities such as ncdump will not assume a
default fill value for byte variables.

Type conversion for fill values is identical to type conversion for
other values: attempting to convert a value from one type to another
type that can't represent the value results in a range error. Such
errors may occur on writing or reading values from a larger type (such
as double) to a smaller type (such as float), if the fill value for
the larger type cannot be represented in the smaller type.

@node NF_RENAME_VAR, NF_VAR_PAR_ACCESS, Fill Values, Variables
@section NF_RENAME_VAR 
@findex NF_RENAME_VAR 

The function NF_RENAME_VAR changes the name of a netCDF variable in an
open netCDF dataset. If the new name is longer than the old name, the
netCDF dataset must be in define mode. You cannot rename a variable to
have the name of any existing variable.

@heading Usage 
@example
INTEGER FUNCTION NF_RENAME_VAR (INTEGER NCID, INTEGER VARID,
                                CHARACTER*(*) NEWNAM)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID.
 
@item NAME
New name for the specified variable.
@end table
 
@heading Errors 

NF_RENAME_VAR returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize
@item
The new name is in use as the name of another variable. 

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 
@end itemize

@heading Example 

Here is an example using NF_RENAME_VAR to rename the variable rh to
rel_hum in an existing netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER  STATUS, NCID
INTEGER  RHID             ! variable ID
   ... 
STATUS = NF_OPEN ('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_REDEF (NCID)  ! enter definition mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_RENAME_VAR (NCID, RHID, 'rel_hum')
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_ENDDEF (NCID) ! leave definition mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_VAR_PAR_ACCESS,  , NF_RENAME_VAR, Variables
@section Change between Collective and Independent Parallel Access: NF_VAR_PAR_ACCESS
@findex NF_VAR_PAR_ACCESS
@cindex NF_VAR_PAR_ACCESS, example

The function NF_VAR_PAR_ACCESS changes whether read/write operations
on a parallel file system are performed collectively or
independently (the default) on the variable. This function can only be called if the
file was created with NF_CREATE_PAR (see @ref{NF_CREATE_PAR}) or opened
with NF_OPEN_PAR (see @ref{NF_OPEN_PAR}).

This function is only available if the netCDF library was built with a
HDF5 library for which --enable-parallel was used, and which was
linked (like HDF5) to MPI libraries.

Calling this function affects only the open file - information about
whether a variable is to be accessed collectively or independently is
not written to the data file. Every time you open a file on a parallel
file system, all variables default to independent operations. The change
a variable to collective lasts only as long as that file is open.

The variable can be changed from collective to independent, and back,
as often as desired.

@heading Usage 

@example
INTEGER NF_VAR_PAR_ACCESS(INTEGER NCID, INTEGER VARID, INTEGER ACCESS);
@end example

@table @code

@item NCID
NetCDF ID, from a previous call to NF_OPEN_PAR (see @ref{NF_OPEN_PAR}) or
NF_CREATE_PAR (see @ref{NF_CREATE_PAR}).
 
@item varid
Variable ID.
 
@item access
NF_INDEPENDENT to set this variable to independent
operations. NF_COLLECTIVE to set it to collective operations.

@end table
 
@heading Return Values

@table @code

@item NF_NOERR
No error.

@item NF_ENOTVAR
No variable found.

@item NF_ENOTNC4
Not a netCDF-4 file.

@item NF_NOPAR
File not opened for parallel access.

@end table

@heading Example
This example comes from test program nf_test/ftst_parallel.F. For this
test to be run, netCDF must have been built with a parallel-enabled
HDF5, and --enable-parallel-tests must have been used when configuring
netcdf.

@example
      retval = nf_var_par_access(ncid, varid, nf_collective)
      if (retval .ne. nf_noerr) stop 2
@end example

@node Attributes, V2 FORTRAN Transition, Variables, Top
@chapter Attributes

@menu
* Attributes Introduction::     
* NF_PUT_ATT_ type::            Create an Attribute
* NF_INQ_ATT Family::           Get Information about an Attribute
* NF_GET_ATT_ type::            
* NF_COPY_ATT::                 
* NF_RENAME_ATT::               
* NF_DEL_ATT::                  
@end menu

@node Attributes Introduction, NF_PUT_ATT_ type, Attributes, Attributes
@section Attributes Introduction

Attributes may be associated with each netCDF variable to specify such
properties as units, special values, maximum and minimum valid values,
scaling factors, and offsets. Attributes for a netCDF dataset are
defined when the dataset is first created, while the netCDF dataset is
in define mode. Additional attributes may be added later by reentering
define mode. A netCDF attribute has a netCDF variable to which it is
assigned, a name, a type, a length, and a sequence of one or more
values. An attribute is designated by its variable ID and name. When
an attribute name is not known, it may be designated by its variable
ID and number in order to determine its name, using the function
NF_INQ_ATTNAME.

The attributes associated with a variable are typically defined
immediately after the variable is created, while still in define
mode. The data type, length, and value of an attribute may be changed
even when in data mode, as long as the changed attribute requires no
more space than the attribute as originally defined.

It is also possible to have attributes that are not associated with
any variable. These are called global attributes and are identified by
using NF_GLOBAL as a variable pseudo-ID. Global attributes are usually
related to the netCDF dataset as a whole and may be used for purposes
such as providing a title or processing history for a netCDF dataset.

Attributes are much more useful when they follow established community
conventions. @xref{Attribute Conventions,,,netcdf, @value{n-man}}.

Operations supported on attributes are:
@itemize

@item
Create an attribute, given its variable ID, name, data type, length, and value. 

@item
Get attribute's data type and length from its variable ID and name. 

@item
Get attribute's value from its variable ID and name. 

@item
Copy attribute from one netCDF variable to another. 

@item
Get name of attribute from its number. 

@item
Rename an attribute. 

@item
Delete an attribute. 
@end itemize

@node NF_PUT_ATT_ type, NF_INQ_ATT Family, Attributes Introduction, Attributes
@section NF_PUT_ATT_ @var{type}
@findex NF_PUT_ATT_ type

The function NF_PUT_ATT_ @var{type} adds or changes a variable attribute or
global attribute of an open netCDF dataset. If this attribute is new,
or if the space required to store the attribute is greater than
before, the netCDF dataset must be in define mode.

@heading Usage 

Although it's possible to create attributes of all types, text and
double attributes are adequate for most purposes.

@example
INTEGER FUNCTION  NF_PUT_ATT_TEXT  (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME, INTEGER LEN,
                                    CHARACTER*(*) TEXT)
INTEGER FUNCTION  NF_PUT_ATT_INT1  (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME, INTEGER XTYPE,
                                    LEN, INTEGER*1 I1VALS(*))
INTEGER FUNCTION  NF_PUT_ATT_INT2  (INTEGER NCID, INTEGER VARID,
                                     CHARACTER*(*) NAME, INTEGER XTYPE,
                                    LEN, INTEGER*2 I2VALS(*))
INTEGER FUNCTION  NF_PUT_ATT_INT   (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME, INTEGER XTYPE,
                                    LEN, INTEGER IVALS(*))
INTEGER FUNCTION  NF_PUT_ATT_REAL  (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME, INTEGER XTYPE,
                                    LEN, REAL RVALS(*))
INTEGER FUNCTION  NF_PUT_ATT_DOUBLE(INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME, INTEGER XTYPE,
                                    LEN, DOUBLE DVALS(*))
INTEGER FUNCTION  NF_PUT_ATT       (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME, INTEGER XTYPE,
                                    LEN, * VALS(*))

@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID of the variable to which the attribute will be assigned or
NF_GLOBAL for a global attribute.
 
@item NAME
Attribute name.  Attribute name conventions are assumed by some netCDF
generic applications, e.g., @samp{units} as the name for a string
attribute that gives the units for a netCDF variable. @xref{Attribute
Conventions,,,netcdf, @value{n-man}}.
 
@item XTYPE
One of the set of predefined netCDF external data types. The type of
this parameter, NF_TYPE, is defined in the netCDF header file. The
valid netCDF external data types are NF_BYTE, NF_CHAR, NF_SHORT,
NF_INT, NF_FLOAT, and NF_DOUBLE. Although it's possible to create
attributes of all types, NF_CHAR and NF_DOUBLE attributes are adequate
for most purposes.
 
@item LEN
Number of values provided for the attribute.
 
@item TEXT
@itemx I1VALS
@itemx I2VALS
@itemx IVALS
@itemx RVALS
@itemx DVALS
@itemx VALS
An array of LEN attribute values. The data should be of a type
appropriate for the function called. You cannot write CHARACTER data
into a numeric attribute or numeric data into a text attribute. For
numeric data, if the type of data differs from the attribute type,
type conversion will occur @xref{Type Conversion,,, netcdf, The
NetCDF Users Guide}.

@end table
 
@heading Errors 

NF_PUT_ATT_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified netCDF type is invalid. 

@item
The specified length is negative. 

@item
The specified open netCDF dataset is in data mode and the specified
attribute would expand.

@item
The specified open netCDF dataset is in data mode and the specified
attribute does not already exist.

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@item
The number of attributes for this variable exceeds NF_MAX_ATTRS. 

@end itemize

@heading Example 

Here is an example using NF_PUT_ATT_DOUBLE to add a variable attribute
named valid_range for a netCDF variable named rh and a global
attribute named title to an existing netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID
INTEGER RHID                 ! variable ID
DOUBLE RHRNGE(2)
DATA RHRNGE /0.0D0, 100.0D0/
   ... 
STATUS = NF_OPEN ('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_REDEF (NCID)     ! enter define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_PUT_ATT_DOUBLE (NCID, RHID, 'valid_range', NF_DOUBLE, &
                            2, RHRNGE)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_PUT_ATT_TEXT (NCID, NF_GLOBAL, 'title', 19, 
                          'example netCDF dataset')
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_ENDDEF (NCID)    ! leave define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_INQ_ATT Family, NF_GET_ATT_ type, NF_PUT_ATT_ type, Attributes
@section NF_INQ_ATT Family
@findex NF_INQ_ATT Family

This family of functions returns information about a netCDF
attribute. All but one of these functions require the variable ID and
attribute name; the exception is NF_INQ_ATTNAME. Information about an
attribute includes its type, length, name, and number. See the
NF_GET_ATT family for getting attribute values.

The function NF_INQ_ATTNAME gets the name of an attribute, given its
variable ID and number. This function is useful in generic
applications that need to get the names of all the attributes
associated with a variable, since attributes are accessed by name
rather than number in all other attribute functions. The number of an
attribute is more volatile than the name, since it can change when
other attributes of the same variable are deleted. This is why an
attribute number is not called an attribute ID.

The function NF_INQ_ATT returns the attribute's type and length. The
other functions each return just one item of information about an
attribute.


@heading Usage 
@example
INTEGER FUNCTION NF_INQ_ATT    (INTEGER NCID, INTEGER VARID,
                                CHARACTER*(*) NAME, INTEGER xtype,
                                INTEGER len)
INTEGER FUNCTION NF_INQ_ATTTYPE(INTEGER NCID, INTEGER VARID,
                                CHARACTER*(*) NAME, INTEGER xtype)
INTEGER FUNCTION NF_INQ_ATTLEN (INTEGER NCID, INTEGER VARID,
                                CHARACTER*(*) NAME, INTEGER len)
INTEGER FUNCTION NF_INQ_ATTNAME(INTEGER NCID, INTEGER VARID,
                                INTEGER ATTNUM, CHARACTER*(*) name)
INTEGER FUNCTION NF_INQ_ATTID  (INTEGER NCID, INTEGER VARID,
                                CHARACTER*(*) NAME, INTEGER attnum)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID of the attribute's variable, or NF_GLOBAL for a global
attribute.
 
@item NAME
Attribute name. For NF_INQ_ATTNAME, this is a pointer to the location
for the returned attribute name.
 
@item xtype
Returned attribute type, one of the set of predefined netCDF external
data types. The valid netCDF external data types are NF_BYTE, NF_CHAR,
NF_SHORT, NF_INT, NF_FLOAT, and NF_DOUBLE.
 
@item len
Returned number of values currently stored in the attribute. For a
string-valued attribute, this is the number of characters in the
string.
 
@item attnum
For NF_INQ_ATTNAME, the input attribute number; for NF_INQ_ATTID, the
returned attribute number. The attributes for each variable are
numbered from 1 (the first attribute) to NATTS, where NATTS is the
number of attributes for the variable, as returned from a call to
NF_INQ_VARNATTS.

(If you already know an attribute name, knowing its number is not very
useful, because accessing information about an attribute requires its
name.)
@end table

@heading Errors 

Each function returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:
@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified attribute does not exist. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@item
For NF_INQ_ATTNAME, the specified attribute number is negative or more
than the number of attributes defined for the specified variable.
@end itemize

@heading Example 

Here is an example using NF_INQ_ATT to find out the type and length of
a variable attribute named valid_range for a netCDF variable named rh
and a global attribute named title in an existing netCDF dataset named
foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS, NCID
INTEGER RHID               ! variable ID
INTEGER VRLEN, TLEN        ! attribute lengths
   ... 
STATUS = NF_OPEN ('foo.nc', NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_ATTLEN (NCID, RHID, 'valid_range', VRLEN)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_INQ_ATTLEN (NCID, NF_GLOBAL, 'title', TLEN)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_GET_ATT_ type, NF_COPY_ATT, NF_INQ_ATT Family, Attributes
@section NF_GET_ATT_ @var{type} 
@findex NF_GET_ATT_ type 

Members of the NF_GET_ATT_ @var{type} family of functions get the value(s)
of a netCDF attribute, given its variable ID and name.

@heading Usage 
@example
INTEGER FUNCTION NF_GET_ATT_TEXT   (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME,
                                    CHARACTER*(*) text)
INTEGER FUNCTION NF_GET_ATT_INT1   (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME,
                                    INTEGER*1 i1vals(*))
INTEGER FUNCTION NF_GET_ATT_INT2   (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME,
                                    INTEGER*2 i2vals(*))
INTEGER FUNCTION NF_GET_ATT_INT    (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME,
                                    INTEGER ivals(*))
INTEGER FUNCTION NF_GET_ATT_REAL   (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME,
                                    REAL rvals(*))
INTEGER FUNCTION NF_GET_ATT_DOUBLE (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME,
                                    DOUBLE dvals(*))
INTEGER FUNCTION NF_GET_ATT        (INTEGER NCID, INTEGER VARID,
                                    CHARACTER*(*) NAME, * vals(*))
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
Variable ID of the attribute's variable, or NF_GLOBAL for a global attribute.
 
@item NAME
Attribute name.
 
@item TEXT
@itemx I1VALS
@itemx I2VALS
@itemx IVALS
@itemx RVALS
@itemx DVALS
@itemx VALS
Returned attribute values. All elements of the vector of attribute
values are returned, so you must provide enough space to hold them. If
you don't know how much space to reserve, call NF_INQ_ATTLEN first to
find out the length of the attribute. You cannot read character data
from a numeric variable or numeric data from a text variable. For
numeric data, if the type of data differs from the netCDF variable
type, type conversion will occur. @xref{Type Conversion,,, netcdf, The
@value{n-man}}.

@end table
 
@heading Errors 

NF_GET_ATT_ @var{type} returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:
@itemize

@item
The variable ID is invalid for the specified netCDF dataset. 

@item
The specified attribute does not exist. 

@item
The specified netCDF ID does not refer to an open netCDF dataset. 

@item
One or more of the attribute values are out of the range of values
representable by the desired type.
@end itemize

@heading Example 

Here is an example using NF_GET_ATT_DOUBLE to determine the values of
a variable attribute named valid_range for a netCDF variable named rh
and a global attribute named title in an existing netCDF dataset named
foo.nc. In this example, it is assumed that we don't know how many
values will be returned, but that we do know the types of the
attributes. Hence, to allocate enough space to store them, we must
first inquire about the length of the attributes.

@example
INCLUDE 'netcdf.inc'
   ... 
PARAMETER (MVRLEN=3)           ! max number of "valid_range" values
PARAMETER (MTLEN=80)           ! max length of "title" attribute
INTEGER STATUS, NCID
INTEGER RHID                   ! variable ID
INTEGER VRLEN, TLEN            ! attribute lengths
DOUBLE PRECISION VRVAL(MVRLEN) ! vr attribute values
CHARACTER*80 TITLE             ! title attribute values
   ... 
STATUS = NF_OPEN ('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! find out attribute lengths, to make sure we have enough space
STATUS = NF_INQ_ATTLEN (NCID, RHID, 'valid_range', VRLEN)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_INQ_ATTLEN (NCID, NF_GLOBAL, 'title', TLEN)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
! get attribute values, if not too big
IF (VRLEN .GT. MVRLEN) THEN
    WRITE (*,*) 'valid_range attribute too big!'
    CALL EXIT
ELSE
    STATUS = NF_GET_ATT_DOUBLE (NCID, RHID, 'valid_range', VRVAL)
    IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
ENDIF
IF (TLEN .GT. MTLEN) THEN
    WRITE (*,*) 'title attribute too big!'
    CALL EXIT
ELSE
    STATUS = NF_GET_ATT_TEXT (NCID, NF_GLOBAL, 'title', TITLE)
    IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
ENDIF
@end example

@node NF_COPY_ATT, NF_RENAME_ATT, NF_GET_ATT_ type, Attributes
@section NF_COPY_ATT 
@findex NF_COPY_ATT 

The function NF_COPY_ATT copies an attribute from one open netCDF
dataset to another. It can also be used to copy an attribute from one
variable to another within the same netCDF.

If used to copy an attribute of user-defined type, then that
user-defined type must already be defined in the target file. In the
case of user-defined attributes, enddef/redef is called for 
ncid_in and ncid_out if they are in define mode. (This is the ensure
that all user-defined types are committed to the file(s) before the
copy is attempted.)

@heading Usage 
@example
INTEGER FUNCTION NF_COPY_ATT (INTEGER NCID_IN, INTEGER VARID_IN,
                              CHARACTER*(*) NAME, INTEGER NCID_OUT,
                              INTEGER VARID_OUT)
@end example

@table @code
@item NCID_IN
The netCDF ID of an input netCDF dataset from which the attribute
will be copied, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID_IN
ID of the variable in the input netCDF dataset from which the
attribute will be copied, or NF_GLOBAL for a global attribute.
 
@item NAME
Name of the attribute in the input netCDF dataset to be copied.
 
@item NCID_OUT
The netCDF ID of the output netCDF dataset to which the attribute
will be copied, from a previous call to NF_OPEN or NF_CREATE. It is
permissible for the input and output netCDF IDs to be the same. The
output netCDF dataset should be in define mode if the attribute to be
copied does not already exist for the target variable, or if it would
cause an existing target attribute to grow.
 
@item VARID_OUT
ID of the variable in the output netCDF dataset to which the
attribute will be copied, or NF_GLOBAL to copy to a global attribute.
@end table
 
@heading Errors 

NF_COPY_ATT returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The input or output variable ID is invalid for the specified netCDF
dataset.

@item
The specified attribute does not exist. 

@item
The output netCDF is not in define mode and the attribute is new for
the output dataset is larger than the existing attribute.

@item
The input or output netCDF ID does not refer to an open netCDF
dataset.
@end itemize

@heading Example 

Here is an example using NF_COPY_ATT to copy the variable attribute
units from the variable rh in an existing netCDF dataset named foo.nc
to the variable avgrh in another existing netCDF dataset named bar.nc,
assuming that the variable avgrh already exists, but does not yet have
a units attribute:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS             ! error status
INTEGER NCID1, NCID2       ! netCDF IDs
INTEGER RHID, AVRHID       ! variable IDs
   ... 
STATUS = NF_OPEN ('foo.nc', NF_NOWRITE, NCID1)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_OPEN ('bar.nc', NF_WRITE, NCID2)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID1, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_INQ_VARID (NCID2, 'avgrh', AVRHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_REDEF (NCID2)  ! enter define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
! copy variable attribute from "rh" to "avgrh"
STATUS = NF_COPY_ATT (NCID1, RHID, 'units', NCID2, AVRHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_ENDDEF (NCID2) ! leave define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_RENAME_ATT, NF_DEL_ATT, NF_COPY_ATT, Attributes
@section NF_RENAME_ATT 
@findex NF_RENAME_ATT 

The function NF_RENAME_ATT changes the name of an attribute. If the
new name is longer than the original name, the netCDF dataset must be
in define mode. You cannot rename an attribute to have the same name
as another attribute of the same variable.

@heading Usage 
@example
INTEGER FUNCTION NF_RENAME_ATT (INTEGER NCID, INTEGER VARID,
                                CHARACTER*(*) NAME,
                                CHARACTER*(*) NEWNAME)
@end example

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE
 
@item VARID
ID of the attribute's variable, or NF_GLOBAL for a global attribute
 
@item NAME
The current attribute name.
 
@item NEWNAME
The new name to be assigned to the specified attribute. If the new
name is longer than the current name, the netCDF dataset must be in
define mode.
@end table
 
@heading Errors 

NF_RENAME_ATT returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:
@itemize

@item
The specified variable ID is not valid. 

@item
The new attribute name is already in use for another attribute of the
specified variable.

@item
The specified netCDF dataset is in data mode and the new name is
longer than the old name.

@item
The specified attribute does not exist. 

@item
The specified netCDF ID does not refer to an open netCDF dataset.
@end itemize

@heading Example 

Here is an example using NF_RENAME_ATT to rename the variable
attribute units to Units for a variable rh in an existing netCDF
dataset named foo.nc:

@example
INCLUDE "netcdf.inc"
   ... 
INTEGER STATUS   ! error status
INTEGER NCID     ! netCDF ID
INTEGER RHID     ! variable ID
   ... 
STATUS = NF_OPEN ("foo.nc", NF_NOWRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, "rh", RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! rename attribute
STATUS = NF_RENAME_ATT (NCID, RHID, "units", "Units")
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node NF_DEL_ATT,  , NF_RENAME_ATT, Attributes
@section NF_DEL_ATT 
@findex NF_DEL_ATT 

The function NF_DEL_ATT deletes a netCDF attribute from an open netCDF
dataset. The netCDF dataset must be in define mode.

@heading Usage 
INTEGER FUNCTION NF_DEL_ATT (INTEGER NCID, INTEGER VARID,
                             CHARACTER*(*) NAME)

@table @code
@item NCID
NetCDF ID, from a previous call to NF_OPEN or NF_CREATE.
 
@item VARID
ID of the attribute's variable, or NF_GLOBAL for a global attribute.
 
@item NAME
The name of the attribute to be deleted.
@end table
 
@heading Errors 

NF_DEL_ATT returns the value NF_NOERR if no errors
occurred. Otherwise, the returned status indicates an error. Possible
causes of errors include:

@itemize

@item
The specified variable ID is not valid. 

@item
The specified netCDF dataset is in data mode. 

@item
The specified attribute does not exist. 

@item
The specified netCDF ID does not refer to an open netCDF dataset.
@end itemize

@heading Example 

Here is an example using NF_DEL_ATT to delete the variable attribute
Units for a variable rh in an existing netCDF dataset named foo.nc:

@example
INCLUDE 'netcdf.inc'
   ... 
INTEGER STATUS            ! error status
INTEGER NCID              ! netCDF ID
INTEGER RHID              ! variable ID
   ... 
STATUS = NF_OPEN ('foo.nc', NF_WRITE, NCID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
STATUS = NF_INQ_VARID (NCID, 'rh', RHID)
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
   ... 
! delete attribute
STATUS = NF_REDEF (NCID)  ! enter define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_DEL_ATT (NCID, RHID, 'Units')
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
STATUS = NF_ENDDEF (NCID) ! leave define mode
IF (STATUS .NE. NF_NOERR) CALL HANDLE_ERR(STATUS)
@end example

@node V2 FORTRAN Transition, Summary of FORTRAN 77 Interface, Attributes, Top
@appendix NetCDF 2 to NetCDF 3 Fortran 77 Transition Guide

@section Overview of FORTRAN interface changes

NetCDF version 3 includes a complete rewrite of the netCDF
library. It is about twice as fast as the previous version. The
netCDF file format is unchanged, so files written with version 3 can
be read with version 2 code and vice versa.

The core library is now written in ANSI C. You must have an ANSI C
compiler to compile this version. The FORTRAN interface is layered on
top of the C interface using a different technique than was used in
netCDF-2.

Rewriting the library offered an opportunity to implement improved C
and FORTRAN interfaces that provide some significant benefits:

@itemize

@item
type safety, by eliminating the need to use type punning in arguments;

@item
automatic type conversions, by eliminating the undesirable coupling
between the language-independent external netCDF types (NF_BYTE, ...,
NF_DOUBLE) and language-dependent internal data types (INT*1, ...,
DOUBLE PRECISION);

@item
support for future enhancements, by eliminating obstacles to the clean
addition of support for packed data and multithreading;

@item
more standard error behavior, by uniformly communicating an error
status back to the calling program in the return value of each
function.

@end itemize

It is not necessary to rewrite programs that use the version 2
FORTRAN interface, because the netCDF-3 library includes a backward
compatibility interface that supports all the old functions, globals,
and behavior. We are hoping that the benefits of the new interface
will be an incentive to use it in new netCDF applications. It is
possible to convert old applications to the new interface
incrementally, replacing netCDF-2 calls with the corresponding
netCDF-3 calls one at a time.

Other changes in the implementation of netCDF result in improved
portability, maintainability, and performance on most platforms. A
clean separation between I/O and type layers facilitates
platform-specific optimizations. The new library no longer uses a
vendor-provided XDR library, which simplifies linking programs that
use netCDF and speeds up data access significantly in most cases.

@section The New FORTRAN Interface

First, here's an example of FORTRAN code that uses the netCDF-2
interface:

@example
! Use a buffer big enough for values of any type
DOUBLE PRECISION DBUF(NDATA)
REAL RBUF(NDATA)
...
EQUIVALENCE (RBUF, DBUF), ...
INT XTYPE     ! to hold the actual type of the data
INT STATUS    ! for error status
! Get the actual data type
CALL NCVINQ(NCID, VARID, ...,XTYPE, ...)
...
! Get the data
CALL NCVGT(NCID, VARID, START, COUNT, DBUF, STATUS)
IF(STATUS .NE. NCNOERR) THEN
   PRINT *, 'Cannot get data, error code =', STATUS
   ! Deal with error
   ...
ENDIF
IF (XTYPE .EQ. NCDOUBLE) THEN
   CALL DANALYZE(DBUF)
ELSEIF (XTYPE .EQ. NCFLOAT) THEN
   CALL RANALYZE(RBUF)
...
ENDIF
@end example

Here's how you might handle this with the new netCDF-3 FORTRAN
interface:

@example
! I want to use doubles for my analysis
DOUBLE PRECISION DBUF(NDATA)
INT STATUS
! So I use a function that gets the data as doubles.
STATUS = NF_GET_VARA_DOUBLE(NCID, VARID, START, COUNT, DBUF)
IF(STATUS .NE. NF_NOERR) THEN
   PRINT *, 'Cannot get data, ', NF_STRERROR(STATUS)
   ! Deal with error
   ...
ENDIF
CALL DANALYZE(DBUF)
@end example

The example above illustrates changes in function names, data type
conversion, and error handling, discussed in detail in the sections
below.

@section Function Naming Conventions

The netCDF-3 Fortran 77 library employs a naming convention intended to
make netCDF programs more readable. For example, the name of the
function to rename a variable is now NF_RENAME_VAR instead of the
previous NCVREN.

All netCDF-3 FORTRAN function names begin with the NF_ prefix. The
second part of the name is a verb, like GET, PUT, INQ (for inquire),
or OPEN. The third part of the name is typically the object of the
verb: for example DIM, VAR, or ATT for functions dealing with
dimensions, variables, or attributes. To distinguish the various I/O
operations for variables, a single character modifier is appended to
VAR:

@itemize

@item
VAR entire variable access

@item
VAR1 single value access

@item
VARA array or array section access

@item
VARS strided access to a subsample of values

@item
VARM mapped access to values not contiguous in memory 

@end itemize

At the end of the name for variable and attribute functions, there is
a component indicating the type of the final argument: TEXT, INT1,
INT2, INT, REAL, or DOUBLE. This part of the function name indicates
the type of the data container you are using in your program:
character string, 1-byte integer, and so on.

Also, all PARAMETER names in the public FORTRAN interface begin with
the prefix NF_. For example, the PARAMETER which was formerly
MAXNCNAM is now NF_MAX_NAME, and the former FILFLOAT is now
NF_FILL_FLOAT.

As previously mentioned, all the old names are still supported for
backward compatibility.

@section Type Conversion

With the new interface, users need not be aware of the external type
of numeric variables, since automatic conversion to or from any
desired numeric type is now available. You can use this feature to
simplify code, by making it independent of external types. The
elimination of type punning prevents some kinds of type errors that
could occur with the previous interface. Programs may be made more
robust with the new interface, because they need not be changed to
accommodate a change to the external type of a variable.

If conversion to or from an external numeric type is necessary, it is
handled by the library. This automatic conversion and separation of
external data representation from internal data types will become
even more important in netCDF version 4, when new external types will
be added for packed data for which there is no natural corresponding
internal type, for example, arrays of 11-bit values.

Converting from one numeric type to another may result in an error if
the target type is not capable of representing the converted
value. (In netCDF-2, such overflows can only happen in the XDR
layer.) For example, a REAL may not be able to hold data stored
externally as an NF_DOUBLE (an IEEE floating-point number). When
accessing an array of values, an NF_ERANGE error is returned if one
or more values are out of the range of representable values, but
other values are converted properly.

Note that mere loss of precision in type conversion does not return
an error. Thus, if you read double precision values into an INTEGER,
for example, no error results unless the magnitude of the double
precision value exceeds the representable range of INTEGERs on your
platform. Similarly, if you read a large integer into a REAL
incapable of representing all the bits of the integer in its
mantissa, this loss There are two new functions in netCDF-3 that
don't correspond to any netCDF-2 functions: NF_INQ_LIBVERS and
NF_STRERROR. The version ation
The previous implementation returned an error when the same dimension
was used more than once in specifying the shape of a variable in
ncvardef. This restriction is relaxed in the netCDF-3 implementation,
because an autocorrelation matrix is a good example where using the
same dimension twice makes sense.

In the new interface, units for the IMAP argument to the NF_PUT_VARM
and NF_GET_VARM families of functions are now in terms of the number
of data elements of the desired internal type, not in terms of bytes
as in the netCDF version-2 mapped access interfaces.

Following is a table of netCDF-2 function names and names of the
corresponding netCDF-3 functions. For parameter lists of netCDF-2
functions, see the netCDF-2 User's Guide.

@table @code

@item NCABOR
NF_ABORT

@item NCACPY
NF_COPY_ATT

@item NCADEL
NF_DEL_ATT

@item NCAGT
NF_GET_ATT_DOUBLE, NF_GET_ATT_REAL, NF_GET_ATT_INT, NF_GET_ATT_INT1,
NF_GET_ATT_INT2

@item NCAGTC
NF_GET_ATT_TEXT

@item NCAINQ
NF_INQ_ATT, NF_INQ_ATTID, NF_INQ_ATTLEN, NF_INQ_ATTTYPE

@item NCANAM
NF_INQ_ATTNAME

@item NCAPT
NF_PUT_ATT_DOUBLE, NF_PUT_ATT_REAL, NF_PUT_ATT_INT,
NF_PUT_ATT_INT1NF_PUT

@end table

@node Summary of FORTRAN 77 Interface, Combined Index, V2 FORTRAN Transition, Top
@appendix Summary of FORTRAN 77 Interface

Input parameters are in upper case, output parameters are in lower
case. The FORTRAN types of all the parameters are listed
alphabetically by parameter name below the function declarations.

@example
CHARACTER*80 FUNCTION  NF_INQ_LIBVERS()
CHARACTER*80 FUNCTION  NF_STRERROR  (NCERR)
INTEGER FUNCTION  NF_CREATE         (PATH, CMODE, ncid)
INTEGER FUNCTION  NF_OPEN           (PATH, MODE, ncid)
INTEGER FUNCTION  NF_SET_FILL       (NCID, FILLMODE, old_mode)
INTEGER FUNCTION  NF_REDEF          (NCID)
INTEGER FUNCTION  NF_ENDDEF         (NCID)
INTEGER FUNCTION  NF_SYNC           (NCID)
INTEGER FUNCTION  NF_ABORT          (NCID)
INTEGER FUNCTION  NF_CLOSE          (NCID)
INTEGER FUNCTION  NF_INQ            (NCID, ndims, nvars, ngatts,
                                     unlimdimid)
INTEGER FUNCTION  NF_INQ_NDIMS      (NCID, ndims)
INTEGER FUNCTION  NF_INQ_NVARS      (NCID, nvars)
INTEGER FUNCTION  NF_INQ_NATTS      (NCID, ngatts)
INTEGER FUNCTION  NF_INQ_UNLIMDIM   (NCID, unlimdimid)
INTEGER FUNCTION  NF_DEF_DIM        (NCID, NAME, LEN, dimid)
INTEGER FUNCTION  NF_INQ_DIMID      (NCID, NAME, dimid)
INTEGER FUNCTION  NF_INQ_DIM        (NCID, DIMID, name, len)
INTEGER FUNCTION  NF_INQ_DIMNAME    (NCID, DIMID, name)
INTEGER FUNCTION  NF_INQ_DIMLEN     (NCID, DIMID, len)
INTEGER FUNCTION  NF_RENAME_DIM     (NCID, DIMID, NAME)

INTEGER FUNCTION  NF_DEF_VAR        (NCID, NAME, XTYPE, NDIMS, DIMIDS, 
                                     varid)
INTEGER FUNCTION  NF_INQ_VAR        (NCID, VARID, name, xtype, ndims, 
                                     dimids, natts)
INTEGER FUNCTION  NF_INQ_VARID      (NCID, NAME, varid)
INTEGER FUNCTION  NF_INQ_VARNAME    (NCID, VARID, name)
INTEGER FUNCTION  NF_INQ_VARTYPE    (NCID, VARID, xtype)
INTEGER FUNCTION  NF_INQ_VARNDIMS   (NCID, VARID, ndims)
INTEGER FUNCTION  NF_INQ_VARDIMID   (NCID, VARID, DIMIDS)
INTEGER FUNCTION  NF_INQ_VARNATTS   (NCID, VARID, natts)
INTEGER FUNCTION  NF_RENAME_VAR     (NCID, VARID, NAME)
INTEGER FUNCTION  NF_PUT_VAR_TEXT   (NCID, VARID, TEXT)
INTEGER FUNCTION  NF_GET_VAR_TEXT   (NCID, VARID, text)
INTEGER FUNCTION  NF_PUT_VAR_INT1   (NCID, VARID, I1VAL)
INTEGER FUNCTION  NF_GET_VAR_INT1   (NCID, VARID, i1val)
INTEGER FUNCTION  NF_PUT_VAR_INT2   (NCID, VARID, I2VAL)
INTEGER FUNCTION  NF_GET_VAR_INT2   (NCID, VARID, i2val)
INTEGER FUNCTION  NF_PUT_VAR_INT    (NCID, VARID, IVAL)
INTEGER FUNCTION  NF_GET_VAR_INT    (NCID, VARID, ival)
INTEGER FUNCTION  NF_PUT_VAR_REAL   (NCID, VARID, RVAL)
INTEGER FUNCTION  NF_GET_VAR_REAL   (NCID, VARID, rval)
INTEGER FUNCTION  NF_PUT_VAR_DOUBLE (NCID, VARID, DVAL)
INTEGER FUNCTION  NF_GET_VAR_DOUBLE (NCID, VARID, dval)
INTEGER FUNCTION  NF_PUT_VAR1_TEXT  (NCID, VARID, INDEX, TEXT)
INTEGER FUNCTION  NF_GET_VAR1_TEXT  (NCID, VARID, INDEX, text)
INTEGER FUNCTION  NF_PUT_VAR1_INT1  (NCID, VARID, INDEX, I1VAL)
INTEGER FUNCTION  NF_GET_VAR1_INT1  (NCID, VARID, INDEX, i1val)
INTEGER FUNCTION  NF_PUT_VAR1_INT2  (NCID, VARID, INDEX, I2VAL)
INTEGER FUNCTION  NF_GET_VAR1_INT2  (NCID, VARID, INDEX, i2val)
INTEGER FUNCTION  NF_PUT_VAR1_INT   (NCID, VARID, INDEX, IVAL)
INTEGER FUNCTION  NF_GET_VAR1_INT   (NCID, VARID, INDEX, ival)
INTEGER FUNCTION  NF_PUT_VAR1_REAL  (NCID, VARID, INDEX, RVAL)
INTEGER FUNCTION  NF_GET_VAR1_REAL  (NCID, VARID, INDEX, rval)
INTEGER FUNCTION  NF_PUT_VAR1_DOUBLE(NCID, VARID, INDEX, DVAL)
INTEGER FUNCTION  NF_GET_VAR1_DOUBLE(NCID, VARID, INDEX, dval)
INTEGER FUNCTION  NF_PUT_VARA_TEXT  (NCID, VARID, START, COUNT, TEXT)
INTEGER FUNCTION  NF_GET_VARA_TEXT  (NCID, VARID, START, COUNT, text)
INTEGER FUNCTION  NF_PUT_VARA_INT1  (NCID, VARID, START, COUNT, I1VALS)
INTEGER FUNCTION  NF_GET_VARA_INT1  (NCID, VARID, START, COUNT, i1vals)
INTEGER FUNCTION  NF_PUT_VARA_INT2  (NCID, VARID, START, COUNT, I2VALS)
INTEGER FUNCTION  NF_GET_VARA_INT2  (NCID, VARID, START, COUNT, i2vals)
INTEGER FUNCTION  NF_PUT_VARA_INT   (NCID, VARID, START, COUNT, IVALS)
INTEGER FUNCTION  NF_GET_VARA_INT   (NCID, VARID, START, COUNT, ivals)
INTEGER FUNCTION  NF_PUT_VARA_REAL  (NCID, VARID, START, COUNT, RVALS)
INTEGER FUNCTION  NF_GET_VARA_REAL  (NCID, VARID, START, COUNT, rvals)
INTEGER FUNCTION  NF_PUT_VARA_DOUBLE(NCID, VARID, START, COUNT, DVALS)
INTEGER FUNCTION  NF_GET_VARA_DOUBLE(NCID, VARID, START, COUNT, dvals)
INTEGER FUNCTION  NF_PUT_VARS_TEXT  (NCID, VARID, START, COUNT, STRIDE,
                                     TEXT)
INTEGER FUNCTION  NF_GET_VARS_TEXT  (NCID, VARID, START, COUNT, STRIDE,
                                     text)
INTEGER FUNCTION  NF_PUT_VARS_INT1  (NCID, VARID, START, COUNT, STRIDE,
                                     I1VALS)
INTEGER FUNCTION  NF_GET_VARS_INT1  (NCID, VARID, START, COUNT, STRIDE,
                                     i1vals)
INTEGER FUNCTION  NF_PUT_VARS_INT2  (NCID, VARID, START, COUNT, STRIDE,
                                     I2VALS)
INTEGER FUNCTION  NF_GET_VARS_INT2  (NCID, VARID, START, COUNT, STRIDE,
                                     i2vals)
INTEGER FUNCTION  NF_PUT_VARS_INT   (NCID, VARID, START, COUNT, STRIDE,
                                     IVALS)
INTEGER FUNCTION  NF_GET_VARS_INT   (NCID, VARID, START, COUNT, STRIDE,
                                     ivals)
INTEGER FUNCTION  NF_PUT_VARS_REAL  (NCID, VARID, START, COUNT, STRIDE,
                                     RVALS)
INTEGER FUNCTION  NF_GET_VARS_REAL  (NCID, VARID, START, COUNT, STRIDE,
                                     rvals)
INTEGER FUNCTION  NF_PUT_VARS_DOUBLE(NCID, VARID, START, COUNT, STRIDE,
                                     DVALS)
INTEGER FUNCTION  NF_GET_VARS_DOUBLE(NCID, VARID, START, COUNT, STRIDE,
                                     dvals)
INTEGER FUNCTION  NF_PUT_VARM_TEXT  (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, TEXT)
INTEGER FUNCTION  NF_GET_VARM_TEXT  (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, text)
INTEGER FUNCTION  NF_PUT_VARM_INT1  (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, I1VALS)
INTEGER FUNCTION  NF_GET_VARM_INT1  (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, i1vals)
INTEGER FUNCTION  NF_PUT_VARM_INT2  (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, I2VALS)
INTEGER FUNCTION  NF_GET_VARM_INT2  (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, i2vals)
INTEGER FUNCTION  NF_PUT_VARM_INT   (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, IVALS)
INTEGER FUNCTION  NF_GET_VARM_INT   (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, ivals)
INTEGER FUNCTION  NF_PUT_VARM_REAL  (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, RVALS)
INTEGER FUNCTION  NF_GET_VARM_REAL  (NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, rvals)
INTEGER FUNCTION  NF_PUT_VARM_DOUBLE(NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, DVALS)
INTEGER FUNCTION  NF_GET_VARM_DOUBLE(NCID, VARID, START, COUNT, STRIDE,
                                     IMAP, dvals)

INTEGER FUNCTION  NF_INQ_ATT        (NCID, VARID, NAME, xtype, len)
INTEGER FUNCTION  NF_INQ_ATTID      (NCID, VARID, NAME, attnum)
INTEGER FUNCTION  NF_INQ_ATTTYPE    (NCID, VARID, NAME, xtype)
INTEGER FUNCTION  NF_INQ_ATTLEN     (NCID, VARID, NAME, len)
INTEGER FUNCTION  NF_INQ_ATTNAME    (NCID, VARID, ATTNUM, name)
INTEGER FUNCTION  NF_COPY_ATT       (NCID_IN, VARID_IN, NAME,
                                     NCID_OUT, VARID_OUT)
INTEGER FUNCTION  NF_RENAME_ATT     (NCID, VARID, CURNAME, NEWNAME)
INTEGER FUNCTION  NF_DEL_ATT        (NCID, VARID, NAME)
INTEGER FUNCTION  NF_PUT_ATT_TEXT   (NCID, VARID, NAME, LEN, TEXT)
INTEGER FUNCTION  NF_GET_ATT_TEXT   (NCID, VARID, NAME, text)
INTEGER FUNCTION  NF_PUT_ATT_INT1   (NCID, VARID, NAME, XTYPE, LEN,
                                     I1VALS)
INTEGER FUNCTION  NF_GET_ATT_INT1   (NCID, VARID, NAME, i1vals)
INTEGER FUNCTION  NF_PUT_ATT_INT2   (NCID, VARID, NAME, XTYPE, LEN,
                                     I2VALS)
INTEGER FUNCTION  NF_GET_ATT_INT2   (NCID, VARID, NAME, i2vals)
INTEGER FUNCTION  NF_PUT_ATT_INT    (NCID, VARID, NAME, XTYPE, LEN,
                                     IVALS)
INTEGER FUNCTION  NF_GET_ATT_INT    (NCID, VARID, NAME, ivals)
INTEGER FUNCTION  NF_PUT_ATT_REAL   (NCID, VARID, NAME, XTYPE, LEN,
                                     RVALS)
INTEGER FUNCTION  NF_GET_ATT_REAL   (NCID, VARID, NAME, rvals)
INTEGER FUNCTION  NF_PUT_ATT_DOUBLE (NCID, VARID, NAME, XTYPE, LEN,
                                     DVALS)
INTEGER FUNCTION  NF_GET_ATT_DOUBLE (NCID, VARID, NAME, dvals)

INTEGER       ATTNUM       ! attribute number
INTEGER       attnum       ! returned attribute number
INTEGER       CMODE        ! NF_NOCLOBBER, NF_SHARE flags expression
INTEGER       COUNT        ! array of edge lengths of block of values
CHARACTER(*)  CURNAME      ! current name (before renaming)
INTEGER       DIMID        ! dimension ID
INTEGER       dimid        ! returned dimension ID
INTEGER       DIMIDS       ! list of dimension IDs
INTEGER       dimids       ! list of returned dimension IDs
DOUBLEPRECISION  DVAL      ! single data value
DOUBLEPRECISION  dval      ! returned single data value
DOUBLEPRECISION  DVALS     ! array of data values
DOUBLEPRECISION  dvals     ! array of returned data values
INTEGER       FILLMODE     ! NF_NOFILL or NF_FILL, for setting fill mode
INTEGER*1     I1VAL        ! single data value
INTEGER*1     I1val        ! returned single data value
INTEGER*1     I1VALS       ! array of data values
INTEGER*1     i1vals       ! array of returned data values
INTEGER*2     I2VAL        ! single data value
INTEGER*2     i2val        ! returned single data value
INTEGER*2     I2VALS       ! array of data values
INTEGER*2     i2vals       ! array of returned data values
INTEGER       IMAP         ! index mapping vector
INTEGER       INDEX        ! variable array index vector
INTEGER       IVAL         ! single data value
INTEGER       ival         ! returned single data value
INTEGER       IVALS        ! array of data values
INTEGER       ivals        ! array of returned data values
INTEGER       LEN          ! dimension or attribute length
INTEGER       len          ! returned dimension or attribute length
INTEGER       MODE         ! open mode, one of NF_WRITE or NF_NOWRITE
CHARACTER(*)  NAME         ! dimension, variable, or attribute name
CHARACTER(*)  name         ! returned dim, var, or att name
INTEGER       natts        ! returned number of attributes
INTEGER       NCERR        ! error returned from NF_xxx function call
INTEGER       NCID         ! netCDF ID of an open netCDF dataset
INTEGER       ncid         ! returned netCDF ID
INTEGER       NCID_IN      ! netCDF ID of open source netCDF dataset
INTEGER       NCID_OUT     ! netCDF ID of open destination netCDF dataset
INTEGER       NDIMS        ! number of dimensions
INTEGER       ndims        ! returned number of dimensions
CHARACTER(*)  NEWNAME      ! new name for dim, var, or att
INTEGER       ngatts       ! returned number of global attributes
INTEGER       nvars        ! returned number of variables
INTEGER       old_mode     ! previous fill mode, NF_NOFILL or NF_FILL,
CHARACTER(*)  PATH         ! name of netCDF dataset
REAL          RVAL         ! single data value
REAL          rval         ! returned single data value
REAL          RVALS        ! array of data values
REAL          rvals        ! array of returned data values
INTEGER       START        ! variable array indices of first value
INTEGER       STRIDE       ! variable array dimensional strides
CHARACTER(*)  TEXT         ! input text value
CHARACTER(*)  text         ! returned text value
INTEGER       unlimdimid   ! returned ID of unlimited dimension
INTEGER       VARID        ! variable ID
INTEGER       varid        ! returned variable ID
INTEGER       VARID_IN     ! variable ID
INTEGER       VARID_OUT    ! variable ID
INTEGER       XTYPE        ! external type: NF_BYTE, NF_CHAR, ... , 
INTEGER       xtype        ! returned external type
@end example

@node Combined Index,  , Summary of FORTRAN 77 Interface, Top
@unnumbered Index

@printindex cp

@bye
End:

