NAME

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

SYNOPSIS

       fitsdiff [OPTION]... FILE1 FILE2

DESCRIPTION

       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.

GENERIC OPTIONS

       -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.

       --no-ignore-blank-cards
              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.

HEADER COMPARISON OPTIONS

       -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.

TABLE COMPARISON OPTIONS

       -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.

EXAMPLES

       % 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).