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DIFF(1) GNU Tools DIFF(1)
NAME
diff - find differences between two files
SYNOPSIS
diff [options] from-file to-file
DESCRIPTION
In the simplest case, diff compares the contents of the two files
from-file and to-file. A file name of - stands for text read from the
standard input. As a special case, diff - - compares a copy of stan-
dard input to itself.
If from-file is a directory and to-file is not, diff compares the file
in from-file whose file name is that of to-file, and vice versa. The
non-directory file must not be -.
If both from-file and to-file are directories, diff compares corre-
sponding files in both directories, in alphabetical order; this com-
parison is not recursive unless the -r or --recursive option is given.
diff never compares the actual contents of a directory as if it were a
file. The file that is fully specified may not be standard input,
because standard input is nameless and the notion of ''file with the
same name'' does not apply.
diff options begin with -, so normally from-file and to-file may not
begin with -. However, -- as an argument by itself treats the remain-
ing arguments as file names even if they begin with -.
Options
Below is a summary of all of the options that GNU diff accepts. Most
options have two equivalent names, one of which is a single letter
preceded by -, and the other of which is a long name preceded by --.
Multiple single letter options (unless they take an argument) can be
combined into a single command line word: -ac is equivalent to -a -c.
Long named options can be abbreviated to any unique prefix of their
name. Brackets ([ and ]) indicate that an option takes an optional
argument.
-lines Show lines (an integer) lines of context. This option does not
specify an output format by itself; it has no effect unless it
is combined with -c or -u. This option is obsolete. For
proper operation, patch typically needs at least two lines of
context.
-a Treat all files as text and compare them line-by-line, even if
they do not seem to be text.
-b Ignore changes in amount of white space.
-B Ignore changes that just insert or delete blank lines.
--brief
Report only whether the files differ, not the details of the
differences.
-c Use the context output format.
-C lines
--context[=lines]
Use the context output format, showing lines (an integer) lines
of context, or three if lines is not given. For proper opera-
tion, patch typically needs at least two lines of context.
--changed-group-format=format
Use format to output a line group containing differing lines
from both files in if-then-else format.
-d Change the algorithm to perhaps find a smaller set of changes.
This makes diff slower (sometimes much slower).
-D name
Make merged if-then-else format output, conditional on the pre-
processor macro name.
-e
--ed Make output that is a valid ed script.
--exclude=pattern
When comparing directories, ignore files and subdirectories
whose basenames match pattern.
--exclude-from=file
When comparing directories, ignore files and subdirectories
whose basenames match any pattern contained in file.
--expand-tabs
Expand tabs to spaces in the output, to preserve the alignment
of tabs in the input files.
-f Make output that looks vaguely like an ed script but has
changes in the order they appear in the file.
-F regexp
In context and unified format, for each hunk of differences,
show some of the last preceding line that matches regexp.
--forward-ed
Make output that looks vaguely like an ed script but has
changes in the order they appear in the file.
-h This option currently has no effect; it is present for Unix
compatibility.
-H Use heuristics to speed handling of large files that have
numerous scattered small changes.
--horizon-lines=lines
Do not discard the last lines lines of the common prefix and
the first lines lines of the common suffix.
-i Ignore changes in case; consider upper- and lower-case letters
equivalent.
-I regexp
Ignore changes that just insert or delete lines that match reg-
exp.
--ifdef=name
Make merged if-then-else format output, conditional on the pre-
processor macro name.
--ignore-all-space
Ignore white space when comparing lines.
--ignore-blank-lines
Ignore changes that just insert or delete blank lines.
--ignore-case
Ignore changes in case; consider upper- and lower-case to be
the same.
--ignore-matching-lines=regexp
Ignore changes that just insert or delete lines that match reg-
exp.
--ignore-space-change
Ignore changes in amount of white space.
--initial-tab
Output a tab rather than a space before the text of a line in
normal or context format. This causes the alignment of tabs in
the line to look normal.
-l Pass the output through pr to paginate it.
-L label
--label=label
Use label instead of the file name in the context format and
unified format headers.
--left-column
Print only the left column of two common lines in side by side
format.
--line-format=format
Use format to output all input lines in in-then-else format.
--minimal
Change the algorithm to perhaps find a smaller set of changes.
This makes diff slower (sometimes much slower).
-n Output RCS-format diffs; like -f except that each command spec-
ifies the number of lines affected.
-N
--new-file
In directory comparison, if a file is found in only one direc-
tory, treat it as present but empty in the other directory.
--new-group-format=format
Use format to output a group of lines taken from just the sec-
ond file in if-then-else format.
--new-line-format=format
Use format to output a line taken from just the second file in
if-then-else format.
--old-group-format=format
Use format to output a group of lines taken from just the first
file in if-then-else format.
--old-line-format=format
Use format to output a line taken from just the first file in
if-then-else format.
-p Show which C function each change is in.
-P When comparing directories, if a file appears only in the sec-
ond directory of the two, treat it as present but empty in the
other.
--paginate
Pass the output through pr to paginate it.
-q Report only whether the files differ, not the details of the
differences.
-r When comparing directories, recursively compare any subdirecto-
ries found.
--rcs Output RCS-format diffs; like -f except that each command spec-
ifies the number of lines affected.
--recursive
When comparing directories, recursively compare any subdirecto-
ries found.
--report-identical-files
-s Report when two files are the same.
-S file
When comparing directories, start with the file file. This is
used for resuming an aborted comparison.
--from-file=file
Compare file to all operands. file can be a directory.
--to-file=file
Compare all operands to file. file can be a directory.
--sdiff-merge-assist
Print extra information to help sdiff. sdiff uses this option
when it runs diff. This option is not intended for users to
use directly.
--show-c-function
Show which C function each change is in.
--show-function-line=regexp
In context and unified format, for each hunk of differences,
show some of the last preceding line that matches regexp.
--side-by-side
Use the side by side output format.
--speed-large-files
Use heuristics to speed handling of large files that have
numerous scattered small changes.
--starting-file=file
When comparing directories, start with the file file. This is
used for resuming an aborted comparison.
--suppress-common-lines
Do not print common lines in side by side format.
-t Expand tabs to spaces in the output, to preserve the alignment
of tabs in the input files.
-T Output a tab rather than a space before the text of a line in
normal or context format. This causes the alignment of tabs in
the line to look normal.
--text Treat all files as text and compare them line-by-line, even if
they do not appear to be text.
-u Use the unified output format.
--unchanged-group-format=format
Use format to output a group of common lines taken from both
files in if-then-else format.
--unchanged-line-format=format
Use format to output a line common to both files in if-then-
else format.
--unidirectional-new-file
When comparing directories, if a file appears only in the sec-
ond directory of the two, treat it as present but empty in the
other.
-U lines
--unified[=lines]
Use the unified output format, showing lines (an integer) lines
of context, or three if lines is not given. For proper opera-
tion, patch typically needs at least two lines of context.
-v
--version
Output the version number of diff.
-w Ignore white space when comparing lines.
-W columns
--width=columns
Use an output width of columns in side by side format.
-x pattern
When comparing directories, ignore files and subdirectories
whose basenames match pattern.
-X file
When comparing directories, ignore files and subdirectories
whose basenames match any pattern contained in file.
-y Use the side by side output format.
SEE ALSO
cmp(1), comm(1), diff3(1), ed(1), patch(1), pr(1), sdiff(1).
DIAGNOSTICS
An exit status of 0 means no differences were found, 1 means some dif-
ferences were found, and 2 means trouble.
GNU Tools 22sep1993 DIFF(1)
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