DIFF
Section: GNU Tools (1)
Updated: 1993-09-22
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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 standard 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 corresponding files in both directories, in
alphabetical 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 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This option is obsolete.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 (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 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 preprocessor
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
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
–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 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.
-r When comparing directories, recursively compare any 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 comparison.
–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.
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 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 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.
Index