.TH gdiffmk 1 "4 October 2023" "groff 1.23.0"
.SH Name
gdiffmk \- mark differences between
.IR groff / nroff / troff
files
.
.
.\" ====================================================================
.\" Legal Terms
.\" ====================================================================
.\"
.\" Copyright (C) 2004-2020 Free Software Foundation, Inc.
.\"
.\" This file is part of gdiffmk, which is part of groff, the GNU roff
.\" type-setting system.
.\"
.\" This program is free software: you can redistribute it and/or modify
.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation, either version 3 of the License, or
.\" (at your option) any later version.
.\"
.\" This program is distributed in the hope that it will be useful, but
.\" WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
.\" General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public License
.\" along with this program.  If not, see
.\" <http://www.gnu.org/licenses/>.
.
.
.\" Save and disable compatibility mode (for, e.g., Solaris 10/11).
.do nr *groff_gdiffmk_1_man_C \n[.cp]
.cp 0
.
.\" Define fallback for groff 1.23's MR macro if the system lacks it.
.nr do-fallback 0
.if !\n(.f           .nr do-fallback 1 \" mandoc
.if  \n(.g .if !d MR .nr do-fallback 1 \" older groff
.if !\n(.g           .nr do-fallback 1 \" non-groff *roff
.if \n[do-fallback]  \{\
.  de MR
.    ie \\n(.$=1 \
.      I \%\\$1
.    el \
.      IR \%\\$1 (\\$2)\\$3
.  .
.\}
.rr do-fallback
.
.
.\" ====================================================================
.SH Synopsis
.\" ====================================================================
.
.SY gdiffmk
.RB [ \-a\~\c
.IR add-mark ]
.RB [ \-c\~\c
.IR change-mark ]
.RB [ \-d\~\c
.IR delete-mark ]
.RB [ \-x\~\c
.IR diff-command ]
.RB [ \-D
.RB [ \-B ]
.RB [ \-M
.IR "mark1 mark2" ]]
.RB [ \-\- ]
.I file1
.I file2
.RI [ output ]
.YS
.
.
.SY gdiffmk
.B \-\-help
.YS
.
.
.SY gdiffmk
.B \-\-version
.YS
.
.
.\" ====================================================================
.SH Description
.\" ====================================================================
.
.I gdiffmk
compares two
.MR roff 7
documents,
.I file1
and
.IR file2 ,
and creates a
.I roff
document consisting of
.I file2
with added margin character
.RB ( .mc )
requests indicating output lines that differ from
.I file1.
.
If the
.I file1
or
.I file2
argument is
.RB \[lq] \- \[rq],
.I gdiffmk
reads the standard input stream for that input.
.
If the
.I output
operand is present,
.I gdiffmk
writes output to a file of that name.
.
If it is
.RB \[lq] \- \[rq]
or absent,
.I gdiffmk
writes output to the standard output stream.
.
.RB \[lq] \- \[rq]
cannot be both an input and output operand.
.
.
.\" ====================================================================
.SH Options
.\" ====================================================================
.
.B \-\-help
displays a usage message
and
.B \-\-version
shows version information;
both exit afterward.
.
.
.TP
.BI \-a\~ add-mark
Use
.I add-mark
for source lines not in
.I file1
but present in
.IR file2 .
.
Default:
.RB \[lq] + \[rq].
.
.
.TP
.B \-B
By default,
the deleted texts marked by the
.B \-D
option end with an added
.I roff
break request,
.BR .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
.BR \-D .
.
.
.TP
.BI \-c\~ change-mark
Use
.I change-mark
for changed source lines.
.
Default:
.RB \[lq] | \[rq].
.
.
.TP
.BI \-d\~ delete-mark
Use the
.I delete-mark
for deleted source lines.
.
Default:
.RB \[lq] * \[rq].
.
.TP
.B \-D
Show the deleted portions from changed and deleted text.
.
.
.TP
.BI \-M\~ "mark1 mark2"
Change the delimiting marks for the
.B \-D
option.
.
It makes no sense to use this option without
.BR \-D .
.
Default delimiting marks:
.RB \[lq] [[ "\[rq] .\|.\|.\& \[lq]" ]] \[rq].
.
.
.TP
.BI \-x\~ diff-command
Use the
.I diff-command
command to perform the comparison of
.I file1
and
.IR file2 .
.
In particular,
.I diff-command
should accept the GNU
.MR diff 1
.B \-D
option.
.
Default:
.BR diff .
.
.
.TP
.B \-\-
Treat all subsequent arguments as file names,
even if they begin with
.RB \[lq] \- \[rq].
.
.
.\" ====================================================================
.SH Bugs
.\" ====================================================================
.
The output is not necessarily compatible with all macro packages
and all preprocessors.
.
A workaround that often overcomes preprocessor problems is to run
.I gdiffmk
on the output of all the preprocessors instead of the input source.
.
.
.LP
.I gdiffmk
relies on the
.B \-D
option of GNU
.I diff
to make a merged \[lq]#ifdef\[rq] output format.
.
Busybox
.I diff
is known to not support it.
.
Also see the
.BI \-x\~ diff-command
option.
.
.
.\" ====================================================================
.SH Authors
.\" ====================================================================
.
.I gdiffmk
was written by
.MT MBianchi@\:Foveal\:.com
Mike Bianchi
.ME ,
now retired.
.
It is maintained by the
.I groff
developers.
.
.
.\" ====================================================================
.SH "See also"
.\" ====================================================================
.
.MR groff 1 ,
.MR nroff 1 ,
.MR gtroff 1 ,
.MR roff 7 ,
.MR diff 1
.
.
.\" Restore compatibility mode (for, e.g., Solaris 10/11).
.cp \n[*groff_gdiffmk_1_man_C]
.do rr *groff_gdiffmk_1_man_C
.
.
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