.. highlightlang:: us

.. index:: nc_attput

.. _nc_attput:

nc_attput
=========

.. us.tag  nc_attput ENGLISH NC_Att

:ref:`nc_attput` changes a variable attribute or global attribute of an open 
nc file. If the attribute is new, or if the space required to store the attribute
is greater than before, the nc file must be in define mode.

.. function::  r = nc_attput(ncid, varid, ssName, nDataType, values)
    r = nc_attput(ncid, varid, ssName, nDataType, values, bOverwrite)

.. us.return

**Return Value**

*r* is -1, if an error occurred.

.. us.params

**Parameters**

.. uparam:: ncid

   Identifies the netCDF file.

.. uparam:: varid

   *varid* is the variable ID of the variable to which the attribute will be
   assigned or -1 for a global attribute. The variable ID starts with 0.

.. uparam:: ssName

   *ssName* is the name of the attribute. It must begin with an alphabetic
   character, followed by zero or more alphanumeric characters including the
   underscore (``_``). Case is significant.

.. uparam:: nDataType

   *nDataType* is the data type of the attribute. The valid netCDF data types are:

   .. list-table::
      :header-rows: 1

      * - Value
        - Meaning
      * - NC_BYTE
        - Eight-bit data
      * - NC_CHAR
        - for representing text strings as arrays of ASCII characters
      * - NC_SHORT
        - 16-Bit integers
      * - NC_LONG
        - 32-Bit integers
      * - NC_FLOAT
        - 32-Bit IEEE floating-point
      * - NC_DOUBLE
        - 64-Bit IEEE floating-point

.. uparam:: values

   *values* is the data value of the appropriate type. *values* can be a column
   or row vector.

.. uparam:: bOverwrite

   If *bOverwrite* is set to TRUE (1) the attribute value will be overwritten.
   If *bOverwrite* is set to FALSE (0), a new attribute will be created
   (Default). A unique name will be created by adding a number to the attribute
   name.

.. us.comment

**Comment**

File must be in definition mode (see:ref:`nc_redef`).

.. seealso::
   :ref:`overview-netcdf-files`,
   :ref:`nc_create`,
   :ref:`nc_attget`

:sub:`id-550528`