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diff - find differences between two files
diff [options]
from-file to-file
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 -.
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with -c or -u. This option is obsolete.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 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.
- --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 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.
cmp(1)
, comm(1)
, diff3(1)
, ed(1)
, patch(1)
, pr(1)
, sdiff(1)
.
An exit status of 0 means no differences were found, 1 means
some differences were found, and 2 means trouble.
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