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gdiffmk(1) — Linux manual page

Name | Synopsis | Description | Options | Exit status | Caveats | Authors | See also | COLOPHON 

gdiffmk(1)               General Commands Manual               gdiffmk(1)

Name         top

       gdiffmk - mark differences between groff/nroff/troff files

Synopsis         top

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

       gdiffmk --help

       gdiffmk --version

Description         top

       gdiffmk compares two roff(7) documents, file1 and file2, and
       writes another, derived from both, to the standard output stream
       (or output-file), adding margin character (mc) requests at places
       in the output where the input documents differ.  gdiffmk does not
       interpret the source documents; it treats roff comments and
       nilpotent changes to formatting as meaningful.  For example, it
       does not know that \h'3m', \h'(1 * 3m)', and \h'3m+0' all mean the
       same thing.  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         top

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

       -a add-mark
              Annotate material absent from file1 but present in file2
              with add-mark (default: “+”).

       -B     Suppress br requests normally inserted by -D option.  Use
              with caution; such requests are the only way to guarantee
              that deletions and small changes are marked.

       -c change-mark
              Annotate material differing between file1 and file2 with
              change-mark (default: “|”).

       -d delete-mark
              Annotate material present in file1 but absent from file2
              with delete-mark (default: “*”).

       -D     Mark changed and deleted material with surrounding
              delimiters.

       -M mark1 mark2
              Use mark1 (default: “[[”) and mark2 (default: “]]”) as
              delimiters when using the -D option.

       -x diff-command
              Use the diff-command program to perform the comparison of
              file1 and file2.  diff-command (default: diff) must accept
              GNU diff(1)'s -D extension option.

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

Exit status         top

       gdiffmk exits with status 0 if the input files are the same; 1 if
       they differ; 2 upon a usage error; 3 if the system's diff(1) or
       sh(1) commands do not support features gdiffmk requires; and 4 if
       the output argument is a duplicate of file1 or file2.

Caveats         top

       The output is not necessarily compatible with all macro packages
       or preprocessors.  A reliable workaround is to run gdiffmk on the
       output of the final preprocessor 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         top

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

See also         top

       groff(1), nroff(1), troff(1), roff(7), diff(1)

COLOPHON         top

       This page is part of the groff (GNU troff) project.  Information
       about the project can be found at 
       ⟨http://www.gnu.org/software/groff/⟩.  If you have a bug report for
       this manual page, see ⟨http://www.gnu.org/software/groff/⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨https://git.savannah.gnu.org/git/groff.git⟩ on 2025-08-11.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2025-08-09.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there is
       a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

groff 1.23.0.3821-a8b3f         2025-08-09                     gdiffmk(1)

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