DIFF(1) (Essential Utilities) DIFF(1)
NAME
diff - differential file comparator
SYNOPSIS
diff [ -efbh ] file1 file2
DESCRIPTION
diff tells what lines must be changed in two files to bring
them into agreement. If file1 (file2) is -, the standard
input is used. If file1 (file2) is a directory, then a file
in that directory with the name file2 (file1) is used. The
normal output contains lines of these forms:
n1 a n3,n4
n1,n2 d n3
n1,n2 c n3,n4
These lines resemble ed commands to convert file1 into
file2. The numbers after the letters pertain to file2. In
fact, by exchanging a for d and reading backward one may
ascertain equally how to convert file2 into file1. As in
ed, identical pairs, where n1 = n2 or n3 = n4, are
abbreviated as a single number.
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 >.
The -b option causes trailing blanks (spaces and tabs) to be
ignored and other strings of blanks to compare equal.
The -e option produces a script of a, c, and d commands for
the editor ed, which will recreate file2 from file1. The -f
option produces a similar script, not useful with ed, in the
opposite order. In connection with -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 ed
scripts ($2,$3,...) made by diff need be on hand. A
``latest version'' appears on the standard output.
Page 1 May 1989
DIFF(1) (Essential Utilities) DIFF(1)
(shift; cat $*; echo '1,$p') | ed - $1
Except in rare circumstances, diff finds a smallest
sufficient set of file differences.
Option -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 -e and -f are
unavailable with -h.
FILES
/tmp/d?????
/usr/lib/diffh for -h
SEE ALSO
bdiff(1), cmp(1), comm(1), ed(1).
DIAGNOSTICS
Exit status is 0 for no differences, 1 for some differences,
2 for trouble.
BUGS
Editing scripts produced under the -e or -f option are naive
about creating lines consisting of a single period (.).
WARNINGS
Missing newline at end of file X
indicates that the last line of file X did not have a new-
line. If the lines are different, they will be flagged and
output; although the output will seem to indicate they are
the same.
Page 2 May 1989