diff - compare two files
diff [-bitw] [-c | -e | -f | -h | -n | -u] file1 file2
diff [-bitw] [-C number | -U number] file1 file2
diff [-bitw] [-D string] file1 file2
diff [-bitw] [-c | -e | -f | -h | -n | -u] [-l] [-r] [-s]
[-S name] directory1 directory2
The diff utility will compare the contents of file1 and
file2 and write to standard output a list of changes neces-
sary to convert file1 into file2. This list should be
minimal. Except in rare circumstances, diff finds a smallest
sufficient set of file differences. No output will be pro-
duced if the files are identical.
The normal output contains lines of these forms:
n1 a n3,n4
n1,n2 d n3
n1,n2 c n3,n4
where n1 and n2 represent lines file1 and n3 and n4
represent lines in file2 These lines resemble ed(1) commands
to convert file1 to file2. By exchanging a for d and reading
backward, file2 can be converted to file1. As in ed, identi-
cal pairs, where n1=n2 or n3=n4, are abbreviated as a single
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 following options are supported:
-b Ignores trailing blanks (spaces and tabs) and treats
other strings of blanks as equivalent.
-i Ignores the case of letters. For example, `A' will
compare equal to `a'.
-t Expands <TAB> characters in output lines. Normal or -c
output adds character(s) to the front of each line
that may adversely affect the indentation of the ori-
ginal source lines and make the output lines difficult
to interpret. This option will preserve the original
-w Ignores all blanks (<SPACE> and <TAB> characters) and
treats all other strings of blanks as equivalent. For
example, `if ( a == b )' will compare equal to
The following options are mutually exclusive:
-c Produces a listing of differences with three lines of
context. With this option, output format is modified
slightly. That is, output begins with identification
of the files involved and their creation dates, then
each change is separated by a line with a dozen *'s.
The lines removed from file1 are marked with '-'. The
lines added to file2 are marked '+'. Lines that are
changed from one file to the other are marked in both
files with '!'.
Produces a listing of differences identical to that
produced by -c with number lines of context.
Creates a merged version of file1 and file2 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
-e Produces a script of only a, c, and d commands for the
editor ed, which will recreate file2 from file1. In
connection with the -e option, 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
(shift; cat $*; echo '1,$p') | ed - $1
-f Produces a similar script, not useful with ed, in the
-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 -c,
-C, -D, -e, -f, and -n are unavailable with -h. diff
does not descend into directories with this option.
-n Produces a script similar to -e, but in the opposite
order and with a count of changed lines on each insert
or delete command.
-u Produces a listing of differences with three lines of
context. The output is similar to that of the -c
option, except that the context is "unified". Removed
and changed lines in file1 are marked by a '-' while
lines added or changed in file2 are marked by a '+'.
Both versions of changed lines appear in the output,
while added, removed, and context lines appear only
once. The identification of file1 and file2 is dif-
ferent, with "---" and "+++" being printed where "***"
and "---" would appear with the -c option. Each change
is separated by a line of the form
@@ -n1,n2 +n3,n4 @@
Produces a listing of differences identical to that
produced by -u with number lines of context.
The following options are used for comparing directories:
-l Produces output in long format. Before the diff, each
text file is piped through pr(1) to paginate it. Other
differences are remembered and summarized after all
text file differences are reported.
-r Applies diff recursively to common subdirectories
-s Reports files that are the identical. These identical
files would not otherwise be mentioned.
Starts a directory diff in the middle, beginning with
the file name.
The following operands are supported:
file2 A path name of a file or directory to be compared. If
either file1 or file2 is -, the standard input will be
used in its place.
A path name of a directory to be compared.
If only one of file1 and file2 is a directory, diff will be
applied to the non-directory file and the file contained in
the directory file with a filename that is the same as the
last component of the non-directory file.
See largefile(5) for the description of the behavior of diff
when encountering files greater than or equal to 2 Gbyte ( 2
Example 1: Typical output of the diff command
In the following command, dir1 is a directory containing a
directory named x, dir2 is a directory containing a direc-
tory named x, dir1/x and dir2/x both contain files named
date.out, and dir2/x contains a file named y:
example% diff -r dir1 dir2
Common subdirectories: dir1/x and dir2/x
Only in dir2/x: y
diff -r dir1/x/date.out dir2/x/date.out
< Mon Jul 2 13:12:16 PDT 1990
> Tue Jun 19 21:41:39 PDT 1990
See environ(5) for descriptions of the following environment
variables that affect the execution of diff: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, LC_TIME, and NLSPATH.
TZ Determines the locale for affecting the timezone used
for calculating file timestamps written with the -C
and -c options.
The following exit values are returned:
0 No differences were found.
1 Differences were found.
>1 An error occurred.
temporary file used for comparison
executable file for -h option
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Availability | SUNWesu |
| CSI | Enabled |
| Interface Stability | Standard |
bdiff(1), cmp(1), comm(1), dircmp(1), ed(1), pr(1), sdiff(
1), attributes(5), environ(5), largefile(5), standards(5)
Editing scripts produced under the -e or -f options are
naive about creating lines consisting of a single period
Missing NEWLINE at end of file indicates that the last line
of the file in question did not have a NEWLINE. If the lines
are different, they will be flagged and output, although the
output will seem to indicate they are the same.
Man(1) output converted with