CDF_ATTPUT

The CDF_ATTPUT procedure writes an attribute entry to a Common Data Format file, or attaches an attribute to a CDF variable. If the specified entry already exists, it is overwritten.

Calling Sequence

CDF_ATTPUT, Id, Attribute, EntryNum, Value

Arguments

Id

The CDF ID, returned from a previous call to CDF_OPEN or CDF_CREATE.

Attribute

A string containing the name of the attribute or the attribute number to be written.

EntryNum

The entry number. If the attribute is variable in scope, this is either the name or number of the variable the attribute is to be associated with. If the attribute is global in scope, this is the actual gEntry. It is the user's responsibility to keep track of valid gEntry numbers. Normally gEntry numbers will begin with 0 or 1 and will increase up to MAXGENTRY (as reported in the GET_ATTR_INFO structure returned by CDF_CONTROL ), but this is not required.

Value

The value(s) to be written.

Keywords

ZVARIABLE

If EntryNum is a variable ID (as opposed to a variable name) and the variable is a zVariable, set this flag to indicate that the variable ID is a zVariable ID. The default is to assume that EntryNum is an rVariable ID. Note: the attribute must have a scope of VARIABLE_SCOPE.

Example

Id= CDF_CREATE('foo', /SUN_ENCODING, /HOST_DECODING, $

    /ROW_MAJOR) ; no dimensions.

dummy= CDF_VARCREATE(id, 'Var1', /CDF_INT4, /REC_VARY)

v2= CDF_VARCREATE(id, 'Var2', /CDF_FLOAT, /REC_NOVARY)

dummy= CDF_ATTCREATE(id, 'Title', /VARIABLE)

global_dummy = CDF_ATTCREATE(id,'Date',/GLOBAL)

dummy= CDF_ATTCREATE(id, 'Att2', /VARIABLE)

CDF_ATTPUT, id, 'Title', 'Var1', 'Temperature at surface'

CDF_ATTPUT, id, 'Title', v2, 'Time of recording'

CDF_ATTPUT, id, 'Date',1,'July 4, 1996'

CDF_ATTPUT, id, 'Att2', 'Var2', FINDGEN(10)

Rename the "Att2" attribute to "Attribute2":

CDF_ATTRENAME, Id, 'Att2', 'Attribute2'

Verify the attribute number (zero-based) of Attribute2

PRINT, CDF_ATTNUM(id, 'Attribute2')

IDL prints:

1

CDF_CLOSE, id ; Close the CDF file. This file is used in the example for CDF_ATTGET.

 

The following example uses the Global attribute "MODS" to keep track of the modification history of a CDF file named mods.cdf .

id = CDF_CREATE('mods.cdf', /CLOBBER)

cid = CDF_ATTCREATE(id, 'MODS', /GLOBAL_SCOPE)

CDF_ATTPUT, id, cid, 0, 'Original Version'

CDF_CLOSE, id

Next, reopen the CDF file and make modifications:

id = CDF_OPEN('mods.cdf')

CDF_CONTROL, id, ATTRIBUTE='MODS', GET_ATTR_INFO=ginfo
; Use CDF_CONTROL to get the MAXGENTRY used.

CDF_ATTPUT, id, cid, ginfo.maxgentry+1,'Second Version'
; Insert the new gEntry at MAXGENTRY+1.

CDF_CLOSE, id

Reopen the CDF file again and make more modifications:

id = CDF_OPEN('mods.cdf')

CDF_CONTROL, id, ATTRIBUTE='MODS', GET_ATTR_INFO=ginfo

CDF_ATTPUT, id, cid, ginfo.maxgentry+1, 'Third Version'

CDF_CLOSE, id

Reopen the CDF file again and make a modification in the MAXGENTRY + 2 spot (skipping an entry number).

id = CDF_OPEN('mods.cdf')

CDF_CONTROL, id, ATTRIBUTE='MODS', GET_ATTR_INFO=ginfo

CDF_ATTPUT, id, cid, ginfo.maxgentry+2, 'Fourth Version'

Now, Examine the CDF file to review its modification history. Since the gENTRY numbers have a gap in them, we can check each attribute with the CDF_ATTEXISTS function. This is a good idea if you do not know for certain that the attribute entries are serially numbered.

CDF_CONTROL, id, ATTRIBUTE='MODS', GET_ATTR_INFO=ginfo

  FOR I=0, ginfo.maxgentry DO BEGIN

    IF CDF_ATTEXISTS(id, cid, I) THEN BEGIN

      CDF_ATTGET, id, cid, I, gatt

      PRINT, I, gatt, FORMAT='("Attribute: MODS (gENTRY #",i1,") = ",A)'

    ENDIF ELSE BEGIN

      PRINT, I, FORMAT='("Attribute: MODS (gENTRY #",i1,") $

        Does not exist")'

    ENDELSE

  ENDFOR

CDF_CLOSE, id

IDL prints:

Attribute: MODS (gENTRY #0) = Original Version

Attribute: MODS (gENTRY #1) = Second Version

Attribute: MODS (gENTRY #2) = Third Version

Attribute: MODS (gENTRY #3) Does not exist

Attribute: MODS (gENTRY #4) = Fourth Version