DIFF(1) User Commands DIFF(1)

NAME

diff - compare two files

SYNOPSIS

diff [-biqtw] [-c | -e | -f | -h | -n | -u] file1 file2
diff [-biqtw] [-C number | -U number] file1 file2
diff [-biqtw] [-D string] file1 file2
diff [-biqtw] [-c | -e | -f | -h | -n | -u] [-l] [-r] [-s] [-S name]
directory1 directory2

DESCRIPTION

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:

n1an3,n4
n1,n2dn3
n1,n2cn3,n4

where n1 and n2 represent lines in 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 backwards, file2 can be converted to
file1. As in ed(1), 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 `>'.

OPTIONS

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'.

-q report only when files differ

-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 original source lines and make
the output lines difficult to interpret. This option will
preserve the original source's indentation.

-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 `if (a==b)'.

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 asterisks (*). 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 `!'.

-C number
Produces a listing of differences identical to that produced by
-c with number lines of context.

-D string
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 file2.

-e Produces a script of only a, c, and d commands for the editor
ed(1), 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 output.

(shift; cat $*; echo a'1,$p') | ed - $1

-f Produces a similar script, not useful with ed(1), in the
opposite order.

-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 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 @@

-U number
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 encountered.

-s Reports files that are identical. These identical files would
not otherwise be mentioned.

-S name
Starts a directory diff in the middle, beginning with the file
name.

OPERANDS

The following operands are supported:

file1
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.

directory1
directory2 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.

USAGE

See largefile(7) for the description of the behavior of diff when
encountering files greater than or equal to 2 Gbyte (2^31 bytes).

FILES

/tmp/d?????
temporary file used for comparison

/usr/lib/diffh
executable file for -h option

EXIT STATUS

The following exit values are returned:

0 No differences were found.

1 Differences were found.

>1 An error occurred.

EXAMPLES

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
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
1c1
< Mon Jul 2 13:12:16 PDT 1990
---
> Tue Jun 19 21:41:39 PDT 1990

ENVIRONMENT VARIABLES

See environ(7) 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.

INTERFACE STABILITY

The command line interface of diff is Committed. The output of diff is
Committed.

SEE ALSO

bdiff(1), cmp(1), comm(1), dircmp(1), ed(1), pr(1), sdiff(1),
attributes(7), environ(7), largefile(7), standards(7)

NOTES

Editing scripts produced under the -e or -f options are na"ive about
creating lines consisting of a single dot `.'.

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.

illumos February 23, 2022 illumos