term% cat index.txt DIFF(1) General Commands Manual DIFF(1)
NAME
diff - differential file comparison
SYNOPSIS
diff [ -l ] [ -r ] [ -s ] [ -cefh ] [ -b ] dir1 dir2
diff [ -cefh ] [ -b ] file1 file2
diff [ -Dstring ] [ -b ] file1 file2
DESCRIPTION
If both arguments are directories, diff sorts the contents of the di‐
rectories by name, and then runs the regular file diff algorithm (de‐
scribed below) on text files which are different. Binary files which
differ, common subdirectories, and files which appear in only one di‐
rectory are listed. Options when comparing directories are:
-l long output format; each text file diff is piped through pr(1)
to paginate it, other differences are remembered and summarized
after all text file differences are reported.
-r causes application of diff recursively to common subdirectories
encountered.
-s causes diff to report files which are the same, which are other‐
wise not mentioned.
-Sname starts a directory diff in the middle beginning with file name.
When run on regular files, and when comparing text files which differ
during directory comparison, 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 file differences. If neither
file1 nor file2 is a directory, then either may be given as `-', in
which case the standard input is used. If file1 is a directory, then a
file in that directory whose file-name is the same as the file-name of
file2 is used (and vice versa).
There are several options for output format; the default output format
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 num‐
bers 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 `>'.
Except for -b, which may be given with any of the others, the following
options are mutually exclusive:
-e producing a script of a, c and d commands for the editor ed,
which will recreate file2 from file1. In connection with -e,
the following shell program may help maintain multiple ver‐
sions 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.
(shift; cat $*; echo '1,$p') ⎪ ed - $1
Extra commands are added to the output when comparing directo‐
ries with -e, so that the result is a sh(1) script for con‐
verting text files which are common to the two directories
from their state in dir1 to their state in dir2.
-f produces a script similar to that of -e, not useful with ed,
and in the opposite order.
-c produces a diff with lines of context. The default is to
present 3 lines of context and may be changed, e.g to 10, by
-c10. With -c the output format is modified slightly: the
output beginning with identification of the files involved and
their creation dates and then each change is separated by a
line with a dozen *'s. The 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 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.
-Dstring causes diff to create a merged version of file1 and file2 on
the standard output, with C preprocessor controls included so
that a compilation of the result without defining string is
equivalent to compiling file1, while defining string will
yield file2.
-b causes trailing blanks (spaces and tabs) to be ignored, and
other strings of blanks to compare equal.
FILES
/tmp/d?????
/usr/lib/diffh for -h
/usr/bin/pr
SEE ALSO
cmp(1), cc(1), comm(1), ed(1), diff3(1), idiff(1)
DIAGNOSTICS
Exit status is 0 for no differences, 1 for some, 2 for trouble.
BUGS
Editing scripts produced under the -e or -f option are naive about cre‐
ating lines consisting of a single `.'.
When comparing directories with the -b option specified, diff first
compares the files ala cmp, and then decides to run the diff algorithm
if they are not equal. This may cause a small amount of spurious out‐
put if the files then turn out to be identical because the only differ‐
ences are insignificant blank string differences.
DIFF(1)