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fitsdiff - compare two FITS image files and report the differences in header keywords and


fitsdiff [OPTION]... FILE1 FILE2


fitsdiff is a command line script based on pyfits to compare two FITS image files and
report the differences in header keywords and data.

FILE1 and FILE2 are the two files to be compared. They may also be wild cards, in such
cases, they must be enclosed by double or single quotes, or they may be directory names.
If both are directory names, all files in each of the directories will be included; if
only one is directory name, then the directory name will be prefixed to the file name(s)
specified by the other argument. For example:

% fitsdiff "*.fits" "/machine/data1"

will compare all FITS files in the current directory to the corresponding files in the
directory /machine/data1.

If the two files are identical within the specified conditions, it will report "No
difference is found." If the value(s) of -c and -k takes the form @filename, list is in
the text file filename, and each line in that text file contains one keyword.

fitsdiff commandline arguments can also be set using the environment variable
FITSDIFF_SETTINGS. If the FITSDIFF_SETTINGS environment variable is present, each argument
present will override the corresponding argument on the commandline. This environment
variable exists to make it easier to change the behavior of fitsdiff on a global level,
such as in a set of regression tests.


-h, --help
Display terse usage information (help).

-q, --quiet
Produce no output and just return a status code.

-n INTEGER, --num-diffs=INTEGER
Max number of data differences (image pixel or table element) to report per
extension (default 10).

-d NUMBER, --difference-tolerance=NUMBER
The relative tolerance for comparison of two numbers, specifically two floating
point numbers. This applies to data in both images and tables, and to floating
point keyword values in headers (default 0.0).

-b, --no-ignore-blanks
Don't ignore trailing blanks (whitespace) in string values. Otherwise trailing
blanks both in header keywords/values and in table column values) are not treated
as significant i.e. without this option 'ABC ' and 'ABC' are considered equivalent.

Don't ignore entirely blank cards in headers. Normally fitsdiff does not consider
blank cards when comparing headers, but this will ensure that even blank cards
match up.

-o FILE, --output-file=FILE
Output results to this file; otherwise results are printed to stdout.


-k KEYWORDS, --ignore-keywords=KEYWORDS
Comma-separated list of keywords not to be compared. Keywords may contain wildcard
patterns. To exclude all keywords, use "*"; make sure to have double or single
quotes around the asterisk.

-c KEYWORDS, --ignore-comments=KEYWORDS
Comma-separated list of keywords whose comments will not be compared. Wildcards
may be used as with --ignore-keywords.


-f COLUMNS, --ignore-fields=COLUMNS
Comma-separated list of fields (i.e. columns) not to be compared. All columns may
be excluded using "*" as with --ignore-keywords.


% fitsdiff -k filename,filtnam1 -n 5 -d 1.e-6 test1.fits test2
This command will compare files test1.fits and test2.fits, report maximum of 5 different
pixels values per extension, only report data values larger than 1.e-6 relative to each
other, and will neglect the different values of keywords FILENAME and FILTNAM1 (or their
very existence).

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