CDF_ATTGET

The CDF_ATTGET procedure reads an attribute entry from a Common Data Format file.

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

A named variable in which the value of the attribute is returned.

Keywords

CDF_TYPE

Set this keyword equal to a named variable which will contain the CDF type of the attribute entry, returned as a scalar string. Possible returned values are: CDF_CHAR, CDF_UCHAR, CDF_INT1, CDF_BYTE, CDF_UINT1, CDF_UINT2, CDF_INT2, CDF_UINT4, CDF_INT4, CDF_REAL4, CDF_FLOAT, CDF_REAL8, CDF_DOUBLE, or CDF_EPOCH. If the type cannot be determined, "UNKNOWN" is returned.

Note that, as is true with variable data, attribute entries of type CDF_INT1, CDF_BYTE, CDF_UINT2, and CDF_UINT4 are converted into IDL supported datatypes (for example, data of type CDF_UINT2, data of the C-type unsigned short, is converted into IDL's INT, a signed integer. (So, an attribute that is 65535 as a CDF_UINT2 will appear as INT = -1 in IDL). In these cases, pay special attention to the return values.

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_OPEN('foo') ; Open the CDF file created in the CDF_ATTPUT example .

CDF_ATTGET, id, 'Att2', 'Var2', x

PRINT, X, FORMAT='("[",9(X,F3.1,","),X,F3.1,"]")'

IDL prints:

[ 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0]
; This is the expected output, since this attribute was created with a call to FINDGEN.

CDF_CLOSE, id ; Close the CDF file.