Research V7 development

Work on file usr/man/man1/diff.1

Synthesized-from: v7

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+.TH DIFF 1 
+.SH NAME
+diff \- differential file comparator
+.SH SYNOPSIS
+.B diff
+[
+.B \-efbh
+] file1 file2
+.SH DESCRIPTION
+.I Diff
+tells what lines must be changed in two files to bring them
+into agreement.
+If
+.I file1
+.RI ( file2 )
+is `\-', the standard input is used.
+If
+.I file1
+.RI ( file2 )
+is a directory, then a file in that directory
+whose file-name is the same as the file-name of 
+.I file2
+.RI ( file1 )
+is used.
+The normal output contains lines of these forms:
+.IP "" 5
+.I n1
+a
+.I n3,n4
+.br
+.I n1,n2
+d
+.I n3
+.br
+.I n1,n2
+c
+.I n3,n4
+.PP
+These lines resemble
+.I ed
+commands to convert
+.I file1
+into
+.IR file2 .
+The numbers after the letters pertain to
+.IR file2 .
+In fact, by exchanging `a' for `d' and reading backward
+one may ascertain equally how to convert 
+.I file2
+into
+.IR file1 .
+As in 
+.I ed,
+identical pairs where
+.I n1
+=
+.I n2
+or
+.I n3
+=
+.I n4
+are abbreviated as a single number.
+.PP
+Following each of these lines come all the lines that are
+affected in the first file flagged by `<', 
+then all the lines that are affected in the second file
+flagged by `>'.
+.PP
+The
+.B \-b
+option causes
+trailing blanks (spaces and tabs) to be ignored
+and other strings of blanks to compare equal.
+.PP
+The
+.B \-e
+option produces a script of
+.I "a, c"
+and 
+.I d
+commands for the editor
+.I ed,
+which will recreate
+.I file2
+from
+.IR file1 .
+The
+.B \-f
+option produces a similar script,
+not useful with
+.I ed,
+in the opposite order.
+In connection with
+.BR \-e ,
+the following shell program may help maintain
+multiple versions of a file.
+Only an ancestral file ($1) and a chain of 
+version-to-version
+.I ed
+scripts ($2,$3,...) made by
+.I diff
+need be on hand.
+A `latest version' appears on
+the standard output.
+.IP "" 5
+(shift; cat $*; echo \'1,$p\') \(bv ed \- $1
+.PP
+Except in rare circumstances,
+.I diff
+finds a smallest sufficient set of file
+differences.
+.PP
+Option
+.B \-h
+does a fast, half-hearted job.
+It works only when changed stretches are short
+and well separated,
+but does work on files of unlimited length.
+Options 
+.B \-e
+and
+.B \-f
+are unavailable with
+.BR \-h .
+.SH FILES
+/tmp/d?????
+.br
+/usr/lib/diffh for 
+.B \-h
+.SH "SEE ALSO"
+cmp(1), comm(1), ed(1)
+.SH DIAGNOSTICS
+Exit status is 0 for no differences, 1 for some, 2 for trouble.
+.SH BUGS
+Editing scripts produced under the
+.BR \-e " or"
+.BR \-f " option are naive about"
+creating lines consisting of a single `\fB.\fR'.