DIFF(1)DIFF(1)NAMEdiff - differential file and directory comparator
SYNOPSISdiff [ -l ] [ -r ] [ -s ] [ -cefhn ] [ -biwt ] dir1 dir2
diff [ -cefhn ] [ -biwtB ] file1 file2
diff [ -Dstring ] [ -biw ] file1 file2
DESCRIPTION
If both arguments are directories, diff sorts the contents of the
directories by name, and then runs the regular file diff algorithm
(described below) on text files which are different. Binary files
which differ, common subdirectories, and files which appear in only one
directory are listed. Options when comparing directories are:
-l long output format; each text file diff is piped through pr(1)
to paginate it, other differences are remembered and summarized
after all text file differences are reported.
-r causes application of diff recursively to common subdirectories
encountered.
-s causes diff to report files which are the same, which are
otherwise not mentioned.
-Sname starts a directory diff in the middle beginning with file name.
When run on regular files, and when comparing text files which differ
during directory comparison, diff tells what lines must be changed in
the files to bring them into agreement. Except in rare circumstances,
diff finds a smallest sufficient set of file differences. If neither
file1 nor file2 is a directory, then either may be given as `-', in
which case the standard input is used. If file1 is a directory, then a
file in that directory whose file-name is the same as the file-name of
file2 is used (and vice versa).
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 ed commands to convert file1 into file2. The
numbers after the letters pertain to file2. In fact, by exchanging `a'
for `d' and reading backward one may ascertain equally how to convert
file2 into 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 `>'.
Except for -b, -w, -i or -t which may be given with any of the others,
the following options are mutually exclusive:
-e produces a script of a, c and d commands for the editor ed,
which will recreate file2 from file1. 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
Extra commands are added to the output when comparing
directories with -e, so that the result is a sh(1) script for
converting text files which are common to the two directories
from their state in dir1 to their state in dir2.
-f produces a script similar to that of -e, not useful with ed,
and in the opposite order.
-n produces a script similar to that of -e, but in the opposite
order and with a count of changed lines on each insert or
delete command. This is the form used by rcsdiff(1).
-c produces a diff with lines of context. The default is to
present 3 lines of context and may be changed, e.g to 10, by
-c10. With -c the output format is modified slightly: the
output beginning with identification of the files involved and
their creation dates and then each change is separated by a
line with a dozen *'s. The lines removed from file1 are
marked with `− '; those added to file2 are marked `+ '. Lines
which are changed from one file to the other are marked in
both files with with `! '.
Changes which lie within <context> lines of each other are
grouped together on output. (This is a change from the
previous ``diff -c'' but the resulting output is usually much
easier to interpret.)
-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.
-Dstring causes diff to create a merged version of file1 and file2 on
the standard output, 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.
-b causes trailing blanks (spaces and tabs) to be ignored, and
other strings of blanks to compare equal.
-w is similar to -b but causes whitespace (blanks and tabs) to be
totally ignored. E.g., ``if ( a == b )'' will compare equal
to ``if(a==b)''.
-i ignores the case of letters. E.g., ``A'' will compare equal
to ``a''.
-t will expand tabs in output lines. Normal or -c output adds
character(s) to the front of each line which may screw up the
indentation of the original source lines and make the output
listing difficult to interpret. This option will preserve the
original source's indentation.
-B forces diff to compare non-binary files containing characters
(such as diacriticals and special symbols) that have the 8th
bit on; otherwise, diff treats such files as binary and
refuses to diff them.
FILES
/tmp/d?????
/usr/lib/diffh for -h
/bin/diff for directory diffs
/bin/pr
SEE ALSOcmp(1), cc(1), comm(1), ed(1), diff3(1)DIAGNOSTICS
Exit status is 0 for no differences, 1 for some, 2 for trouble.
BUGS
Editing scripts produced under the -e or -f option are naive about
creating lines consisting of a single `.'.
When comparing directories with the -b, -w or -i options specified,
diff first compares the files ala cmp, and then decides to run the diff
algorithm if they are not equal. This may cause a small amount of
spurious output if the files then turn out to be identical because the
only differences are insignificant blank string or case differences.
4th Berkeley Distribution May 19, 1986 DIFF(1)
