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Accessing header items by index
There are two HDR routines that allow you to access header items using
an index number. Header item index numbers run from 1 through to the
maximum number of items available. These facilities can be used to
list all the header items, or to test for the existence of items with
particular names.
The following program snippet shows how to list all the header items
associated with an image.
It uses the HDR_NUMB subroutine to query the number of
items. The complete example is called
hdrlist.f - see §
.
* See how many header items are available.
CALL HDR_NUMB( 'IN', ' ', '*', N, ISTAT ) [1]
DO 1 I = 1, N
* Get the name of the I'th header item.
CALL HDR_NAME( 'IN', ' ', I, ITEM, ISTAT ) [2]
* Get its value.
CALL HDR_IN( 'IN', ' ', ITEM, 1, VALUE, ISTAT ) [3]
* And write it out.
WRITE( *, '( 1X, 3A )' ) ITEM ,' = ', VALUE [4]
1 CONTINUE
The following notes refer to the numbered statements:
- 1.
- The subroutine HDR_NUMB counts the number of header items
or the number of occurrences of an item. The '*' argument indicates
that all the header items are to be counted. If an
item name was given the number of occurrences of that item would be
returned (zero if none exist).
- 2.
- Item names may be queried by using an index number. This provides a
method of getting all the names when the exact contents of a header
item source are not known.
- 3.
- HDR_IN returns the value of the header item as a
character string.
- 4.
- The name and value of the header item are written out.
Next: Special behaviour of FITS headers
Up: More advanced header access
Previous: Using header items from different sources
IMG Simple Image Data Access
Starlink User Note 160
P.W. Draper
R.F. Warren-Smith
3 March 2003
E-mail:P.W.Draper@durham.ac.uk
Copyright © 2000-2003 Council for the Central Laboratory of the Research Councils