'\" te
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.TH DIFFMK 1 "Sep 14, 1992"
.SH NAME
diffmk \- mark differences between versions of a troff input file
.SH SYNOPSIS
.LP
.nf
\fBdiffmk\fR \fIoldfile\fR \fInewfile\fR \fImarkedfile\fR
.fi

.SH DESCRIPTION
.sp
.LP
\fBdiffmk\fR compares two versions of a file and creates a third version that
includes "change mark" (\fB\&.mc\fR) commands for \fBnroff\fR(1) and
\fBtroff\fR(1). \fIoldfile\fR and \fInewfile\fR are the old and new versions of
the file. \fBdiffmk\fR generates \fImarkedfile\fR, which, contains the text
from \fInewfile\fR with  \fBtroff\fR(1) "change mark" requests (\fB\&.mc\fR)
inserted where  \fInewfile\fR differs from  \fIoldfile\fR. When
\fImarkedfile\fR is formatted, changed or inserted text is shown by  \fB|\fR at
the right margin of each line. The position of deleted text is shown by a
single \fB*\fR.
.SH USAGE
.sp
.LP
See \fBlargefile\fR(5) for the description of the behavior of \fBdiffmk\fR when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
.SH EXAMPLES
.LP
\fBExample 1 \fRAn example of the \fBdiffmk\fR command.
.sp
.LP
\fBdiffmk\fR can also be used in conjunction with the proper  \fBtroff\fR
requests to produce program listings with marked changes. In the following
command line:

.sp
.in +2
.nf
\fBexample% diffmk old.c new.c marked.c ; nroff reqs marked.c | pr\fR
.fi
.in -2
.sp

.sp
.LP
the file \fBreqs\fR contains the following \fBtroff\fR requests:

.sp
.in +2
.nf
\&.pl \|1
\&.ll \|77
\&.nf
\&.eo
\&.nh
.fi
.in -2
.sp

.sp
.LP
which eliminate page breaks, adjust the line length, set no-fill mode, ignore
escape characters, and turn off hyphenation, respectively.

.sp
.LP
If the characters  \fB|\fR and \fB*\fR are inappropriate, you might run
\fImarkedfile\fR through  \fBsed\fR(1) to globally change them.

.SH SEE ALSO
.sp
.LP
\fBdiff\fR(1), \fBnroff\fR(1), \fBsed\fR(1), \fBtroff\fR(1),
\fBattributes\fR(5), \fBlargefile\fR(5)
.SH BUGS
.sp
.LP
Aesthetic considerations may dictate manual adjustment of some output. File
differences involving only formatting requests may produce undesirable output,
that is, replacing \fB\&.sp\fR by \fB\&.sp 2\fR will produce a "change mark" on
the preceding or following line of output.