fitsdiff - compare two FITS image files and report the differences in header
keywords and data.
]... FILE1 FILE2
is a command line script based on pyfits to compare two FITS
image files and report the differences in header keywords and data.
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"
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
takes the form @filename
, list is in the text file filename
each line in that text file contains one keyword.
commandline arguments can also be set using the environment
. If the FITSDIFF_SETTINGS
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,
- Max number of data differences (image pixel or table
element) to report per extension (default 10).
- -d 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
- -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 results to this file; otherwise results are printed
- -k 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
- -c KEYWORDS,
- Comma-separated list of keywords whose comments will not be
compared. Wildcards may be used as with --ignore-keywords.
% fitsdiff -k filename,filtnam1 -n 5 -d 1.e-6 test1.fits test2
- -f COLUMNS,
- Comma-separated list of fields (i.e. columns) not to be
compared. All columns may be excluded using "*" as with
This command will compare files test1.fits
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
(or their very