diff(1)

Synopsis

diff [-bitw] [-C number] filename1 filename2

diff [-bitw] [-D string] filename1 filename2

diff [-bitw] [-c | -e | -f | -h | -n] [-l] [-r] [-s] [-S name] directory1 directory2

Description

   n1an3,n4
   n1,n2dn3
   n1,n2cn3,n4

These lines resemble ed(1) commands to convert filename1 into filename2. The numbers after the letters pertain to filename2. In fact, by exchanging a for d and reading backward one may ascertain equally how to convert filename2 into filename1. 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 ``>''.

-b

Ignores trailing blanks (spaces and tabs) and treats other strings of blanks as equivalent. The LC_CTYPE environment variable determines what characters are treated as blanks. (See ctype(3C) and LANG on environ(5).)

-i

Ignores the case of letters; for example, ``A'' will be treated as equal to ``a''. This option is also influenced by the locale value in the LC_CTYPE environment variable.

-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. The LC_CTYPE environment variable is used in correctly formatting the data, and so must specify a locale that defines the same codesets as used in the input data.

-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: 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 dates are in the format that output from date "+%a %b %e %T %Y" produces. This is affected by the LC_TIME environment variable. (see date(1) and LANG on environ(5)). The lines removed from filename1 are marked with '--'; those added to filename2 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. The form of number is affected by the LC_NUMERIC environment variable. (see strtol(3C) and LANG on environ(5)).

-e

Produces a script of a, c, and d commands for the editor ed, which will recreate filename2 from filename1. 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 standard output.

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

Except in rare circumstances, diff finds a smallest sufficient set of file differences.

-f

Produces a similar script, not useful with ed, 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 -e and -f are unavailable with -h.

-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.

-D string

Creates a merged version of filename1 and filename2 with C preprocessor controls included so that a compilation of the result without defining string is equivalent to compiling filename1, while defining string will yield filename2.

The following options are used for comparing directories:

-l

Produce 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 would not otherwise be mentioned.

-S name

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

Error codes

indicates that the last line of file X did not have a new-line. If the lines are different, they will be flagged and output; although the output will seem to indicate they are the same.

Files

/tmp/d?????

/usr/lib/diffh

for -h

/usr/bin/pr

/usr/lib/locale/locale/LC_MESSAGES/uxcore.abi

language-specific message file (see LANG on environ(5)).

References

Notices