diff - differential file and directory comparator
diff [ -l ] [ -r ] [ -s ] [ -cuefhn ] [ -biwt ] dir1 dir2
diff [ -cuefhn ] [ -biwt ] file1 file2
diff [ -Dstring ] [ -biw ] file1 file2
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
-s causes diff to report files which are the same, which are otherwise
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
-u Like -c, but produces a diff in "unified diff" format. This
format marks lines that are only in file1 with a `-', lines only
in file2 with a `+', with context lines surrounding these
changes. This format is much shorter than a context diff, and
much preferred by people who have learned to read it.
-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
-i ignores the case of letters. E.g., ``A'' will compare equal to
-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.
cmp(1), cc(1), comm(1), ed(1), diff3(1).
Exit status is 0 for no differences, 1 for some, 2 for trouble.