diff(1)diff(1)Namediff - differential file comparator
Syntaxdiff [options] dir1 dir2
diff [options] file1 file2
The command compares the contents of files or groups of files, and
lists any differences it finds. When run on regular files, and when
comparing text files that differ during directory comparison, tells
what lines must be changed in the files to bring them into agreement.
Except in rare circumstances, finds a smallest sufficient set of file
differences. If neither file1 nor file2 is a directory, then either
can be specified as `-', in which case the standard input is used. If
file1 is a directory, then a file in that directory whose filename is
the same as the filename of file2 is used and likewise if file2 is a
If both arguments are directories, sorts the contents of the directo‐
ries by name, and then runs the regular file algorithm on text files
that are different. Binary files that differ, common subdirectories,
and files that appear in only one directory are listed.
The following options are used when comparing directories:
-l Displays the output in long format. Each text file is piped
through to paginate it; other differences are summarized
after all text file differences are reported.
-n Produces a script similar to that of -e, but in reverse order
and with a count of changed lines on each insert or delete
-r Recursively checks files in common subdirectories.
-s Displays names of files that are the same.
-Sname Starts a directory in the middle beginning with the specified
Except for the -b, i, t, and w options, which may be given with any of
the others, the following formatting options are mutually exclusive:
-b Ignores trailing blanks and other strings of blanks and
treats such portions as equal.
-c Displays three context lines with each output line. For
backwards compatibility, -cn causes n number of context
-C n Displays specified number of context lines with each output
line. With -c or -C the output format is modified slightly:
the output begins with identification of the files involved
and their creation dates and then each change is separated by
a line with a dozen asterisks (*). The lines removed from
file1 are marked with minus sign (-); those added to file2
are marked plus sign (+). Lines that are changed from one
file to the other are marked in both files with an exclama‐
tion point (!).
Changes within n context lines of each other are grouped
together in the output. This results in output that is usu‐
ally much easier to interpret.
-Dstring Causes to create a merged version of file1 and file2 on the
standard output. With C preprocessor controls included, a
compilation of the result without defining string is equiva‐
lent to compiling file1, while defining string will yield
-e Writes output to an script. In connection with -e, the fol‐
lowing shell program can help maintain multiple versions of a
file. Only an ancestral file ($1) and a chain of version-to-
version scripts ($2,$3,...) made by need be available. A
latest version message appears on the standard output.
(shift; cat $*; echo ´1,$p´) ⎪ ed - $1
If you specify -e when comparing directories the result is a
script for converting text files that are common to the two
directories from their state in dir1 to their state in dir2.
-f Writes the output in reverse order to a script.
-h Makes a hasty comparison. It works only when changed por‐
tions are short and well separated, but does work on files of
-i Ignores the case of letters. For example 'A' will compare
equal to `a'.
-t Expand tabs in output lines. Normal or -c output adds char‐
acter(s) to the front of each line which may affect the
indentation of the original source lines and make the output
listing difficult to interpret. This option will preserves
the original indentation.
-w Causes whitespace (blanks and tabs) to be totally ignored.
For example, `if ( a == b )' will compare equal to
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 commands to convert file1 into file2. The numbers
after the letters pertain to file2. In fact, by exchanging `a' for `d'
and reading backward you can tell how to convert file2 into file1. As
in identical 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 a left angle bracket (<). Then all the lines
that are affected in the second file are listed, flagged by a right
angle bracket (>).
Editing scripts produced under the -e or -f option have trouble creat‐
ing lines consisting of a single period (.).
When comparing directories with the -b, i, t, or w options specified,
first compares the files as does, and then runs the algorithm if they
are not equal. If the only differences are in the blank strings, may
report these as differences.
Exit status is 0 for no differences, 1 for some differences,and 2 if
the specified file cannot be found.
cc(1), cmp(1), comm(1), diff3(1), ed(1)diff(1)