GNU Astronomy Utilities manual

4.1.2 Arguments

In GNU Astronomy Utilities, the names of the input data files and ASCII tables are mostly specified as arguments, you can generally specify them in any order unless otherwise stated for a particular program. Everything particular about how a program treats arguments, is explained under the “Invoking ProgramName” section for that program.

Generally, if there is a standard file name extension for a particular format, that filename extension is used to separate the kinds of arguments. The list below shows what astronomical data formats are recognized based on their file name endings. If the program doesn’t accept any other data format, any other argument that doesn’t end with the specified extentions below is considered to be a text file (usually catalogs). For example ConvertType accepts other data formats.

• .fits: The standard file name ending of a FITS image.
• .fits.Z: A FITS image compressed with compress.
• .fits.gz: A FITS image compressed with GNU zip (gzip).
• .fits.fz: A FITS image compressed with fpack.
• .imh: IRAF format image file.

Through out this manual and in the command line outputs, whenever we want to generalize all such astronomical data formats in a text place holder, we will use ASTRdata, we will assume that the extension is also part of this name. Any file ending with these names is directly passed on to CFITSIO to read. Therefore you don’t necessarily have to have these files on your computer, they can also be located on an FTP or HTTP server too, see the CFITSIO manual for more information.

CFITSIO has its own error reporting techniques, if your input file(s) cannot be opened, or read, those errors will be printed prior to the final error by Gnuastro.

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GNU Astronomy Utilities manual, November 2015.