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NetCDF User's Guide for FORTRAN

8 Attributes

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.

Operations supported on attributes are:

Create an attribute, given its variable ID, name, data type, length, and value.
Get attribute's data type and length from its variable ID and name.
Get attribute's value from its variable ID and name.
Copy attribute from one netCDF variable to another.
Get name of attribute from its number.
Rename an attribute.
Delete an attribute.

8.1 Attribute Conventions

Names commencing with underscore ('_') are reserved for use by the netCDF library. Most generic applications that process netCDF datasets assume standard attribute conventions and it is strongly recommended that these be followed unless there are good reasons for not doing so. Below we list the names and meanings of recommended standard attributes that have proven useful. Note that some of these (e.g. units, valid_range, scale_factor) assume numeric data and should not be used with character data.

`units`	A character string that specifies the units used for the variable's data. Unidata has developed a freely-available library of routines to convert between character string and binary forms of unit specifications and to perform various useful operations on the binary forms. This library is used in some netCDF applications. Using the recommended units syntax permits data represented in conformable units to be automatically converted to common units for arithmetic operations. See Appendix A "Units," page 113, for more information.
`long_name`	A long descriptive name. This could be used for labeling plots, for example. If a variable has no `long_name` attribute assigned, the variable name should be used as a default.
`valid_min`	A scalar specifying the minimum valid value for this variable.
`valid_max`	A scalar specifying the maximum valid value for this variable.
`valid_range`	A vector of two numbers specifying the minimum and maximum valid values for this variable, equivalent to specifying values for both `valid_min` and `valid_max` attributes. Any of these attributes define the valid range. The attribute `valid_range` must not be defined if either `valid_min` or `valid_max` is defined. Generic applications should treat values outside the valid range as missing. The type of each `valid_range`, `valid_min` and `valid_max` attribute should match the type of its variable (except that for `byte` data, these can be of a signed integral type to specify the intended range). If neither `valid_min`, `valid_max` nor `valid_range` is defined then generic applications should define a valid range as follows. If the data type is byte and `_FillValue` is not explicitly defined, then the valid range should include all possible values. Otherwise, the valid range should exclude the `_FillValue` (whether defined explicitly or by default) as follows. If the `_FillValue` is positive then it defines a valid maximum, otherwise it defines a valid minimum. For integer types, there should be a difference of 1 between the `_FillValue` and this valid minimum or maximum. For floating point types, the difference should be twice the minimum possible (1 in the least significant bit) to allow for rounding error.
`scale_factor`	If present for a variable, the data are to be multiplied by this factor after the data are read by the application that accesses the data.
`add_offset`	If present for a variable, this number is to be added to the data after it is read by the application that accesses the data. If both `scale_factor` and `add_offset` attributes are present, the data are first scaled before the offset is added. The attributes `scale_factor` and `add_offset` can be used together to provide simple data compression to store low-resolution floating-point data as small integers in a netCDF dataset. When scaled data are written, the application should first subtract the offset and then divide by the scale factor. When `scale_factor` and `add_offset` are used for packing, the associated variable (containing the packed data) is typically of type byte or short, whereas the unpacked values are intended to be of type float or double. The attributes `scale_factor` and `add_offset` should both be of the type intended for the unpacked data, e.g. float or double.
`_FillValue`	The `_FillValue` attribute specifies the fill value used to pre-fill disk space allocated to the variable. Such pre-fill occurs unless nofill mode is set using `NF_SET_FILL`. See Section 5.12 "Set Fill Mode for Writes: nc_set_fill," page 39, for details. The fill value is returned when reading values that were never written. If `_FillValue` is defined then it should be scalar and of the same type as the variable. It is not necessary to define your own `_FillValue` attribute for a variable if the default fill value for the type of the variable is adequate. However, use of the default fill value for data type byte is not recommended. Note that if you change the value of this attribute, the changed value applies only to subsequent writes; previously written data are not changed. Generic applications often need to write a value to represent undefined or missing values. The fill value provides an appropriate value for this purpose because it is normally outside the valid range and therefore treated as missing when read by generic applications. It is legal (but not recommended) for the fill value to be within the valid range. See Section 7.16 "Fill Values," page 78, for more information.
`missing_value`	This attribute is not treated in any special way by the library or conforming generic applications, but is often useful documentation and may be used by specific applications. The `missing_value` attribute can be a scalar or vector containing values indicating missing data. These values should all be outside the valid range so that generic applications will treat them as missing.
`signedness`	Deprecated attribute, originally designed to indicate whether byte values should be treated as signed or unsigned. The attributes `valid_min` and `valid_max` may be used for this purpose. For example, if you intend that a byte variable store only nonnegative values, you can use `valid_min = 0` and `valid_max = 255`. This attribute is ignored by the netCDF library.
`C_format`	A character array providing the format that should be used by C applications to print values for this variable. For example, if you know a variable is only accurate to three significant digits, it would be appropriate to define the `C_format` attribute as `"%.3g"`. The `ncdump` utility program uses this attribute for variables for which it is defined. The format applies to the scaled (internal) type and value, regardless of the presence of the scaling attributes `scale_factor` and `add_offset`.
`FORTRAN_format`	A character array providing the format that should be used by FORTRAN applications to print values for this variable. For example, if you know a variable is only accurate to three significant digits, it would be appropriate to define the `FORTRAN_format` attribute as `"(G10.3)"`.
`title`	A global attribute that is a character array providing a succinct description of what is in the dataset.
`history`	A global attribute for an audit trail. This is a character array with a line for each invocation of a program that has modified the dataset. Well-behaved generic netCDF applications should append a line containing: date, time of day, user name, program name and command arguments.
`Conventions`	If present, '`Conventions`' is a global attribute that is a character array for the name of the conventions followed by the dataset, in the form of a string that is interpreted as a directory name relative to a directory that is a repository of documents describing sets of discipline-specific conventions. This permits a hierarchical structure for conventions and provides a place where descriptions and examples of the conventions may be maintained by the defining institutions and groups. The conventions directory name is currently interpreted relative to the directory `pub/netcdf/Conventions/` on the host machine `ftp.unidata.ucar.edu`. Alternatively, a full URL specification may be used to name a WWW site where documents that describe the conventions are maintained.
	For example, if a group named NUWG agrees upon a set of conventions for dimension names, variable names, required attributes, and netCDF representations for certain discipline-specific data structures, they may store a document describing the agreed-upon conventions in a dataset in the `NUWG/` subdirectory of the Conventions directory. Datasets that followed these conventions would contain a global `Conventions` attribute with value `"NUWG"`.
	Later, if the group agrees upon some additional conventions for a specific subset of NUWG data, for example time series data, the description of the additional conventions might be stored in the `NUWG/Time_series/` subdirectory, and datasets that adhered to these additional conventions would use the global `Conventions` attribute with value `"NUWG/Time_series"`, implying that this dataset adheres to the NUWG conventions and also to the additional NUWG time-series conventions.

8.2 Create an Attribute: `NF_PUT_ATT_` type

The function NF_PUT_ATT_ 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.

Usage

Although it's possible to create attributes of all types, text and double attributes are adequate for most purposes.

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(*))

`NCID`	NetCDF ID, from a previous call to `NF_OPEN` or `NF_CREATE`.
`VARID`	Variable ID.
`NAME`	Attribute name. Must begin with an alphabetic character, followed by zero or more alphanumeric characters including the underscore ('`_`'). Case is significant. Attribute name conventions are assumed by some netCDF generic applications, e.g., `units` as the name for a string attribute that gives the units for a netCDF variable. A table of conventional attribute names is presented in the earlier chapter on the netCDF interface.
`XTYPE`	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`. Although it's possible to create attributes of all types, `NF_CHAR` and `NF_DOUBLE` attributes are adequate for most purposes.
`LEN`	The number of values provided for the attribute, or the length of the text attribute for `NF_PUT_ATT_TEXT`.
`TEXT, I1VALS, I2VALS, IVALS,RVALS, or DVALS`	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 (see Section 3.3 "Type Conversion," page 24, for details).

Errors

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

The variable ID is invalid for the specified netCDF dataset.
The specified netCDF type is invalid.
The specified length is negative.
The specified open netCDF dataset is in data mode and the specified attribute would expand.
The specified open netCDF dataset is in data mode and the specified attribute does not already exist.
The specified netCDF ID does not refer to an open netCDF dataset.
The number of attributes for this variable exceeds NF_MAX_ATTRS.

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:

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)

8.3 Get Information about an Attribute: `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.

Usage

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)

`NCID`	NetCDF ID, from a previous call to `NF_OPEN` or `NF_CREATE`.
`VARID`	Variable ID of the attribute's variable, or `NF_GLOBAL` for a global attribute.
`NAME`	Attribute name, input except that for `NF_INQ_ATTNAME`, this is where the attribute name is returned.
`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`.
`len`	Returned number of values currently stored in the attribute. For a string-valued attribute, this is the number of characters in the string.
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.)

Errors

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

The variable ID is invalid for the specified netCDF dataset.
The specified attribute does not exist.
The specified netCDF ID does not refer to an open netCDF dataset.
For NF_INQ_ATTNAME, the specified attribute number is negative or more than the number of attributes defined for the specified variable.

Example

Here is an example using NF_INQ_ATTLEN to inquire about the lengths of an attribute named valid_range for a netCDF variable named rh and a global attribute named title in an existing netCDF dataset named foo.nc:

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)

8.4 Get Attribute's Values: `NF_GET_ATT_` type

Members of the NF_GET_ATT_ type family of functions get the value(s) of a netCDF attribute, given its variable ID and name.

Usage

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(*))

`NCID`	NetCDF ID, from a previous call to `NF_OPEN` or `NF_CREATE`.
`VARID`	Variable ID of the attribute's variable, or `NF_GLOBAL` for a global attribute.
`NAME`	Attribute name.
`text, i1vals, i2vals, ivals,rvals, or dvals`	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 (see Section 3.3 "Type Conversion," page 24, for details).

Errors

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

The variable ID is invalid for the specified netCDF dataset.
The specified attribute does not exist.
The specified netCDF ID does not refer to an open netCDF dataset.
One or more of the attribute values are out of the range of values representable by the desired type.

Example

Here is an example using NF_GET_ATT_DOUBLE to determine the values of an 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, so we first inquire about the length of the attributes to make sure we have enough space to store them:

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

8.5 Copy Attribute from One NetCDF to Another: `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.

Usage

INTEGER FUNCTION NF_COPY_ATT (INTEGER NCID_IN, INTEGER VARID_IN,
                              CHARACTER*(*) NAME, INTEGER NCID_OUT,
                              INTEGER VARID_OUT)

`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`.
`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.
`NAME`	Name of the attribute in the input netCDF dataset to be copied.
`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.
`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.

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:

The input or output variable ID is invalid for the specified netCDF dataset.
The specified attribute does not exist.
The output netCDF is not in define mode and the attribute is new for the output dataset is larger than the existing attribute.
The input or output netCDF ID does not refer to an open netCDF dataset.

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:

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)

8.6 Rename an Attribute: `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.

INTEGER FUNCTION NF_RENAME_ATT (INTEGER NCID, INTEGER VARID,
                                CHARACTER*(*) NAME,
                                CHARACTER*(*) NEWNAME)

`NCID`	NetCDF ID, from a previous call to `NF_OPEN` or `NF_CREATE`
`VARID`	ID of the attribute's variable, or `NF_GLOBAL` for a global attribute
`NAME`	The current attribute name.
`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.

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:

The specified variable ID is not valid.
The new attribute name is already in use for another attribute of the specified variable.
The specified netCDF dataset is in data mode and the new name is longer than the old name.
The specified attribute does not exist.
The specified netCDF ID does not refer to an open netCDF dataset.

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:

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)

8.7 Delete an Attribute: `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.

Usage

INTEGER FUNCTION NF_DEL_ATT (INTEGER NCID, INTEGER VARID,
                             CHARACTER*(*) NAME)

`NCID`	NetCDF ID, from a previous call to `NF_OPEN` or `NF_CREATE`.
`VARID`	ID of the attribute's variable, or `NF_GLOBAL` for a global attribute.
`NAME`	The original attribute name.

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:

The specified variable ID is not valid.
The specified netCDF dataset is in data mode.
The specified attribute does not exist.
The specified netCDF ID does not refer to an open netCDF dataset.

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:

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)

8 Attributes

8.1 Attribute Conventions

8.2 Create an Attribute: NF_PUT_ATT_ type

Usage

Errors

Example

8.3 Get Information about an Attribute: NF_INQ_ATT Family

Usage

Errors

Example

8.4 Get Attribute's Values: NF_GET_ATT_ type

Usage

Errors

Example

8.5 Copy Attribute from One NetCDF to Another: NF_COPY_ATT

Usage

Errors

Example

8.6 Rename an Attribute: NF_RENAME_ATT

Errors

Example

8.7 Delete an Attribute: NF_DEL_ATT

Usage

Errors

Example

<http://www.unidata.ucar.edu>

8.2 Create an Attribute: `NF_PUT_ATT_` type

8.3 Get Information about an Attribute: `NF_INQ_ATT` Family

8.4 Get Attribute's Values: `NF_GET_ATT_` type

8.5 Copy Attribute from One NetCDF to Another: `NF_COPY_ATT`

8.6 Rename an Attribute: `NF_RENAME_ATT`

8.7 Delete an Attribute: `NF_DEL_ATT`