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Astronomical Data Analysis Software and Systems VII
ASP Conference Series, Vol. 145, 1998
Editors: R. Albrecht, R. N. Hook and H. A. Bushouse
Nelson Zarate
National Optical Astronomy Observatories
Tucson, AZ 85719 (zarate@noao.edu)
Abstract:
The Multiple Extension FITS (MEF) file interface is an IRAF library providing
facilities for general file operations upon FITS multi-extension files. The
MEF library has been used as the basis for a set of new IRAF tasks providing
file level operations for multi-extension files. These operations include
functions like listing extensions, extracting, inserting, or appending
extensions, deleting extensions, and manipulating extension headers.
MEF supports extensions of any type since it is a file level interface and
does not attempt to interpret the contents of a particular extension type.
Other IRAF interfaces such as IMIO (the FITS image kernel) and STSDAS TABLES
are available for dealing with specific types of extensions such as the IMAGE
extension or binary tables.
The Multiple Extensions FITS (MEF) interface consists of a number
of routines to mainly read a FITS Primary Data Unit or an Extension
Unit and manipulate the data at a file level. It is up to the application
to take care of any details regarding data structuring and manipulation.
For example, the MEF interface will read a BINTABLE extension and give to
the calling program a set of parameters like dimensionality, datatype, header
buffer pointer and data portion offset from the beginning of the file.
Currently the routines available to an SPP program are:
-
mef = mef_open (fitsfile, acmode, oldp)
-
mef_rdhdr (mef, group, extname, extver)
-
mef_rdhdr_exnv (mef, extname, extver)
-
mef_wrhdr (mefi, mefo, in_phdu)
-
[irdb]val = mefget[irdb] (mef, keyword)
-
mefgstr (mef, keyword, outstr, maxch)
-
mef_app_file (mefi, mefo)
-
mef_copy_extn (mefi, mefo, group)
-
mef_dummyhdr (fd, hdrfname)
[irdb]: int, real, double, boolean.
Initializes the MEF interface. Should be the
first routine to be called when performing operations on FITS files
using this set of routines. Returns a pointer to the MEF structure.
- fitsfile
- Pathname to the FITS file to be open. The general syntax is:
dir$root.extn[group]
- dir: Directory name where the file resides
- root: Rootname
- extn: (optional) Extension name -- can be any extension string
- group: Extension number to be opened
The `[group]' string is optional and is not part of the disk
filename. It is used to specified which extension number to
open. The extension number is zero based -- zero for the primary
extension, 1 for the first extension, and so on.
- acmode
- The access mode of the file. The possible values are:
READ_ONLY, READ_WRITE, APPEND, NEW_FILE
- oldp
- Not used. Reserve for future use.
Read the FITS header of a MEF file that matches the EXTNAME or
EXTVER keyword values or if not specified, read the extension
number `group'. If no extension is found an error is posted.
After reading the header the file pointer is positioned at the end
of the last data FITS block (2880 bytes).
- mef
- The MEF pointer returned by mef_open. When the routine returns, all of
the elements of the MEF structure will have values belonging
to the header just read.
- group
- The extension number to be read -- zero for the Primary Data Unit,
1 for the first extension, and so on. If you want to find out an
extension by the value of extname and/or extver then `group'
should be -1.
- extname
- The string that will match the EXTNAME value of any extension. The
first match is the extension header returned.
- extver
- The integer value that will match the EXTVER value of any extension.
If `extname' is not null then both values need to match before
the routine returns. If there are no values to match then `extver'
should be INDEFL.
Read extension number `group'. If the extension number does not
exist, an error is posted.
- mef
- The MEF pointer returned by mef_open. When the routine returns, all of
the elements of the MEF structure will have values belonging
to the header just read.
- group
- The extension number to be read -- zero for the Primary Data Unit,
1 for the first extension, and so on.
Read group based on the Extname and Extver values. If the group
is not encountered, an error is posted.
- mef
- The MEF pointer returned by mef_open. When the routine returns, all of
the elements of the MEF structure will have values belonging
to the header just read.
- extname
- The string that will match the EXTNAME value of any extension. The
first match is the extension header returned.
- extver
- The integer value that will match the EXTVER value of any extension.
If `extname' is not null then both values need to match before
the routine returns. If there are no value to match then `extver'
should be INDEFL.
Append the header from an input PHU or EHU to output file.
- mefi
- The input file MEF pointer returned by mef_open. The header
should have been read by now.
- mefo
- The output file MEF pointer returned by mef_open.
- in_phdu
- Boolean value (true, false) stating whether the input header
is the primary header or not.
[irdb]: integer, real, double or boolean.
Get a FITS header keyword value of the specified datatype; for
example `imgeti (mef, ``NCOMB'')' will return an integer value
from the keyword `NCOMB'.
- mef
- The input file MEF pointer returned by mef_open. The header
should have been read by now.
- keyword
- The input string (case insensitive) keyword from which to return
its value.
Get the string value of a FITS encoded card. Strip leading
and trailing whitespace and any quotes.
- mef
- The input file MEF pointer returned by mef_open. The header
should have been read by now.
- keyword
- The input string (case insensitive) keyword from which to return
its value.
- outstr
- The output string with the value of input keyword.
- maxch
- Length in chars of outstr.
Appends a FITS file to an output file. If the file does
not exist, a dummy Primary Header Unit is first created.
- mefi
- The input file MEF pointer returned by mef_open. The header
should have been read by now.
- mefo
- The output file MEF pointer returned by mef_open.
Copy a FITS extension given by its number `group' into an
output file. If the file does not exists, this extension becomes
a Primary Header Data Unit of the output FITS file. If the
output file already exists, the input extension gets appended.
- mefi
- The input file MEF pointer returned by mef_open. The header
should have been read by now.
- mefo
- The output file MEF pointer returned by mef_open.
- group
- The input extension number to be appended to the output file.
Write a dummy Primary Header Unit with no data to a new file.
Optionally a header file with user keywords can be used.
- fd
- The output file descriptor.
- hdr_fname
- The header filename. This is text file with a FITS header syntax
that will be appended to the file. Each FITS card does not have to
be 80 characters long. The routine takes care of the correct
padding.
© Copyright 1998 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA
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