diff(1) USER COMMANDS diff(1)
NAME
diff - differential file comparator
SYNOPSIS
diff [ -bitw ] [ -c|-e|-f |-h|-n ] filename1 filename2
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
diff tells what lines must be changed in two files to bring
them into agreement. If filename1 (filename2) is -, the
standard input is used. If filename1 (filename2) is a
directory, then a file in that directory with the name
filename2 (filename1) is used. The normal output 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 filename1 into
filename2. The numbers after the letters pertain to
filename2. In fact, by exchanging a for d and reading back-
ward 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.
-i Ignores the case of letters; for example, `A' will com-
pare equal to `a'.
-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)'.
1
diff(1) USER COMMANDS diff(1)
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
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.
-e Produces a script of a, c, and d commands for the edi-
tor 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 suffi-
cient 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 compi-
lation 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
2
diff(1) USER COMMANDS diff(1)
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 the identical; these would not
otherwise be mentioned.
-S name
Starts a directory diff in the middle, beginning with
the file name.
FILES
/tmp/d?????
/usr/lib/diffh for -h
/usr/bin/pr
SEE ALSO
bdiff(1), cmp(1), comm(1), ed(1), pr(1).
DIAGNOSTICS
Exit status is 0 for no differences, 1 for some differences,
2 for trouble.
NOTES
Editing scripts produced under the -e or -f option are naive
about creating lines consisting of a single period (.).
Missing newline at end of file X
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.
3