DIFF(1)DIFF(1)NAMEdiff - compare two files
SYNOPSISdiff [-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 necessary 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
produced 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, 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 following options are supported:
Ignores trailing blanks (spaces and tabs) and treats other
strings of blanks as equivalent.
Ignores the case of letters. For example, `A' will compare equal
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 original source lines and make the output
lines difficult to interpret. This option will preserve the
original source's indentation.
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 `if(a==b)'.
The following options are mutually exclusive:
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 pro‐
duced by -c with number lines of context.
Creates a merged version of file1 and file2 with C pre‐
processor controls included so that a compilation of the
result without defining string is equivalent to compiling
file1, while defining string will yield file2.
Produces a script of only a, c, and d commands for the
editor ed, which will recreate file2 from file1. In con‐
nection 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 output.
(shift; cat $*; echo a´1,$p') | ed − $1
Produces a similar script, not useful with ed, in the
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.
Produces a script similar to -e, but in the opposite order
and with a count of changed lines on each insert or delete
Produces a listing of differences with three lines of con‐
text. 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 different, 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 pro‐
duced by -u with number lines of context.
The following options are used for comparing directories:
Produces output in long format. Before the diff, each text
file is piped through pr(1) to paginate it. Other differ‐
ences are remembered and summarized after all text file
differences are reported.
Applies diff recursively to common subdirectories encoun‐
Reports files that are identical. These identical files
would not otherwise be mentioned.
Starts a directory diff in the middle, beginning with the
The following operands are supported:
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-
See largefile(5) for the description of the behavior of diff when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
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 directory named x, dir1/x and
dir2/x both contain files named date.out, and dir2/x contains a file
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.
Determines the locale for affecting the timezone used for calcu‐
lating file timestamps written with the -C and -c options.
The following exit values are returned:
No differences were found.
Differences were found.
An error occurred.
temporary file used for comparison
executable file for -h option
See attributes(5) for descriptions of the following attributes:
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
│CSI │ Enabled │
│Interface Stability │ Standard │
SEE ALSObdiff(1), cmp(1), comm(1), dircmp(1), ed(1), pr(1), sdiff(1),
attributes(5), environ(5), largefile(5), standards(5)NOTES
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.
Sep 22, 2004 DIFF(1)