DIFF(1) DIFF(1)
NAME
diff, diff3 - differential file comparison
SYNOPSIS
diff [ option ... ] file1 file2
diff3 [ -ex3 ] file1 file2 file3
DESCRIPTION
When run on regular files diff tells what lines must be
changed in the files to bring them into agreement. Except
in rare circumstances, diff finds a smallest sufficient set
of differences. If neither file is a directory, then one
may be `-', meaning the standard input. If one file is a
directory, then a file in that directory with basename the
same as that of the other file is used.
If both files are directories, similarly named files in the
two directories are compared by the method of diff for text
files and cmp(1) otherwise. Options when comparing directo-
ries are:
-r Apply diff recursively to similarly named subdirecto-
ries.
-s Report files that are the same (normally not men-
tioned).
There are several options for output format; the default
output format contains lines of these forms:
n1a n3,n4
n1,n2d n3
n1,n2c 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 `>'.
-e Produce a script of `a', `c', and `d' for ed(1) to
recreate file2 from file1. When comparing directories,
produce a sh(1) script to convert text files common to
the two directories.
DIFF(1) DIFF(1)
-cn Include n extra lines of context with each set of dif-
ferences. The output format is modified: the output
begins with identification of the files involved and
their creation dates and changes are separated by lines
of *'s. Lines removed from file1 are marked with `-';
those added to file2 are marked `+'. Lines which are
changed from one file to the other are marked in both
files with `!'.
-h Do a fast, half-hearted job, useful only when changed
stretches are short and well separated, but does work
on files of unlimited length.
-b Ignore trailing blanks (spaces and tabs) and treat
other strings of blanks as if they were a single space.
-B Ignore all blanks.
Diff3 compares three versions of a file and publishes the
various disagreeing ranges of text. One of the following
indicators introduces each reported difference.
==== All three files differ.
====f
File f differs, where f is 1, 2, or 3.
Disagreeing fragments from the three files follow the ====
line, each identified by a diff-like range indication:
f:n1a
File f lacks text that other files have; their text
would be appended after line n1.
f:n1,n2c
f:n1c
Lines n1 through n2 (or line n1 only) of file f would
have to be changed to agree with some other file. The
original contents follow, unless a higher-numbered file
has the same contents.
Under option -e, diff3 publishes a script for ed(1) that
will incorporate into file1 all changes between file2 and
file3, i.e. the changes that normally would be flagged ====
and ====3. Option -x (-3) produces a script to incorporate
only changes flagged ==== (====3).
EXAMPLES
(cat diff0-1 diff1-2 diff2-3; echo '1,$p') | ed -
file0 >file3
An ancestral `file0' has been kept along with a chain
of version-to-version difference files made thus: `diff
DIFF(1) DIFF(1)
-e file0 file1 >diff0-1'. The shell command recon-
structs the latest version.
if diff3 mod1 old mod2 | grep -s '^====$'
then :
else (diff3 -e mod1 old mod2; echo '1,$p') | ed - mod1 >new
fi
Compare two different modified versions with an old
file. If no modifications interfere with each other
(grep finds no ==== lines), make a new file incorporat-
ing both modifications.
FILES
for -h
SEE ALSO
cmp(1), comm(1), ed(1), idiff(1)
DIAGNOSTICS
Diff yields exit status is 0 for no differences, 1 for some,
2 for trouble.
BUGS
Text lines that consist of a single `.' will defeat options
-e, -x, and -3.
Superfluous output may result for files that differ only in
insignificant blanks when comparing directories under option
-b.
Option -c is unpardonably bizarre.