gdiffmk(1)                  General Commands Manual                 gdiffmk(1)

Name
       gdiffmk - mark differences between groff/nroff/troff files

Synopsis
       gdiffmk [-a add-mark] [-c change-mark] [-d delete-mark]
               [-x diff-command] [-D [-B] [-M mark1 mark2]] [--] file1 file2
               [output]

       gdiffmk --help

       gdiffmk --version

Description
       gdiffmk compares two roff(7) documents, file1 and file2, and creates a
       roff document consisting of file2 with added margin character (.mc)
       requests indicating output lines that differ from file1.  If the file1
       or file2 argument is “-”, gdiffmk reads the standard input stream for
       that input.  If the output operand is present, gdiffmk writes output to
       a file of that name.  If it is “-” or absent, gdiffmk writes output to
       the standard output stream.  “-” cannot be both an input and output
       operand.

Options
       --help displays a usage message and --version shows version
       information; both exit afterward.

       -a add-mark
              Use add-mark for source lines not in file1 but present in file2.
              Default: “+”.

       -B     By default, the deleted texts marked by the -D option end with
              an added roff break request, .br, to ensure that the deletions
              are marked properly.  This is the only way to guarantee that
              deletions and small changes get flagged.  This option directs
              the program not to insert these breaks; it makes no sense to use
              it without -D.

       -c change-mark
              Use change-mark for changed source lines.  Default: “|”.

       -d delete-mark
              Use the delete-mark for deleted source lines.  Default: “*”.

       -D     Show the deleted portions from changed and deleted text.

       -M mark1 mark2
              Change the delimiting marks for the -D option.  It makes no
              sense to use this option without -D.  Default delimiting marks:
              “[[” ... “]]”.

       -x diff-command
              Use the diff-command command to perform the comparison of file1
              and file2.  In particular, diff-command should accept the GNU
              diff(1) -D option.  Default: diff.

       --     Treat all subsequent arguments as file names, even if they begin
              with “-”.

Bugs
       The output is not necessarily compatible with all macro packages and
       all preprocessors.  A workaround that often overcomes preprocessor
       problems is to run gdiffmk on the output of all the preprocessors
       instead of the input source.

       gdiffmk relies on the -D option of GNU diff to make a merged “#ifdef”
       output format.  Busybox diff is known to not support it.  Also see the
       -x diff-command option.

Authors
       gdiffmk was written by Mike Bianchi <MBianchi@Foveal.com>, now retired.
       It is maintained by the groff developers.

See also
       groff(1), nroff(1), gtroff(1), roff(7), diff(1)

groff 1.23.0                      5 July 2023                       gdiffmk(1)