DIFF(1) 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 directories by name, and then runs the regular file
diff algorithm (described below) on text files which are
different. Binary files which differ, common subdirecto-
ries, and files which appear in only one directory 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 differ-
ences are reported.
-r causes application of diff recursively to common subdi-
rectories encountered.
-s causes diff to report files which are the same, which
are otherwise 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 agree-
ment. 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 direc-
tory, 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 numbers after the letters pertain to file2. In
DIFF(1) DIFF(1)
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 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 stan-
dard output.
(shift; cat $*; echo '1,$p') | ed - $1
Extra commands are added to the output when compar-
ing directories with -e, so that the result is a
sh(1) script for converting 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
DIFF(1) DIFF(1)
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 trou-
ble.
BUGS
Editing scripts produced under the -e or -f option are naive
about creating 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 output if the files then
turn out to be identical because the only differences are
insignificant blank string differences.