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diff command help
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 standard input to itself.
If from-file is a directory and to-file is not, diff com
pares 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 com
pares corresponding files in both directories, in alpha
betical order; this comparison 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 remaining 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 let
ter 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-u. This option is obsolete.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 opera
tion, 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.
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 operation, patch typically needs
at least two lines of context.
--changed-group-format=format
Use format to output a line group containing dif
fering lines from both files in if-then-else for
mat.
-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 preprocessor macro name.
-e
--ed Make output that is a valid ed script.
--exclude=pattern
When comparing directories, ignore files and subdi
rectories whose basenames match pattern.
--exclude-from=file
When comparing directories, ignore files and subdi
rectories whose basenames match any pattern con
tained 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.
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 suf
fix.
-i Ignore changes in case; consider upper- and lower-
case letters equivalent.
-I regexp
Ignore changes that just insert or delete lines
that match regexp.
--ifdef=name
Make merged if-then-else format output, conditional
on the preprocessor 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 regexp.
--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
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 specifies the number of lines affected.
-N
--new-file
In directory comparison, if a file is found in only
one directory, 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 second 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 second 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.
subdirectories found.
--rcs Output RCS-format diffs; like -f except that each
command specifies the number of lines affected.
--recursive
When comparing directories, recursively compare any
subdirectories 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 compar
ison.
--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 compar
ison.
--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.
-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 second 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 operation, 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 for
mat.
-x pattern
When comparing directories, ignore files and subdi
rectories whose basenames match pattern.
-X file
When comparing directories, ignore files and subdi
rectories whose basenames match any pattern con
tained 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 differences were found, and 2 means trouble.
Comments - most recent first
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