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, 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                                       3 June 2025                                        gdiffmk(1)