13.1 Options to diff

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.

-a

--text

Treat all files as text and compare them line-by-line, even if they do not seem to be text. See Binary Files and Forcing Text Comparisons.

-b

--ignore-space-change

Ignore changes in amount of white space. See Suppressing Differences in Blank and Tab Spacing.

-B

--ignore-blank-lines

Ignore changes that just insert or delete blank lines. See Suppressing Differences Whose Lines Are All Blank.

--binary

Read and write data in binary mode. See Binary Files and Forcing Text Comparisons.

-c

Use the context output format, showing three lines of context. See Context Format.

--color [=when] ¶

Specify whether to use color for distinguishing different contexts, like header, added or removed lines. when may be omitted, or one of:

• none Do not use color at all. This is the default when no –color option is specified.
• auto Use color only if standard output is a terminal.
• always Always use color.

Specifying --color and no when is equivalent to --color=auto.

-C lines

--context[=lines]

Use the context output format, showing lines (an integer) lines of context, or three if lines is not given. See Context Format. For proper operation, patch typically needs at least two lines of context.

For compatibility diff also supports an obsolete option syntax -lines that has effect when combined with -c, -p, or -u. New scripts should use -U lines (-C lines) instead.

--changed-group-format=format

Use format to output a line group containing differing lines from both files in if-then-else format. See Line Group Formats.

-d

--minimal

Change the algorithm perhaps find a smaller set of changes. This makes diff slower (sometimes much slower). See diff Performance Tradeoffs.

-D name

--ifdef=name

Make merged ‘#ifdef’ format output, conditional on the preprocessor macro name. See Merging Files with If-then-else.

-e

--ed

Make output that is a valid ed script. See ed Scripts.

-E

--ignore-tab-expansion

Ignore changes due to tab expansion. See Suppressing Differences in Blank and Tab Spacing.

-f

--forward-ed

Make output that looks vaguely like an ed script but has changes in the order they appear in the file. See Forward ed Scripts.

-F regexp

--show-function-line=regexp

In context and unified format, for each hunk of differences, show some of the last preceding line that matches regexp. See Showing Lines That Match Regular Expressions.

--from-file=file

Compare file to each operand; file may be a directory.

--help

Output a summary of usage and then exit.

--horizon-lines=lines

Do not discard the last lines lines of the common prefix and the first lines lines of the common suffix. See diff Performance Tradeoffs.

-i

--ignore-case

Ignore changes in case; consider upper- and lower-case letters equivalent. See Suppressing Case Differences.

-I regexp

--ignore-matching-lines=regexp

Ignore changes that just insert or delete lines that match regexp. See Suppressing Differences Whose Lines All Match a Regular Expression.

--ignore-file-name-case

Ignore case when comparing file names. For example, recursive comparison of d to e might compare the contents of d/Init and e/inIt. At the top level, ‘diff d inIt’ might compare the contents of d/Init and inIt. See Comparing Directories.

-l

--paginate

Pass the output through pr to paginate it. See Paginating diff Output.

-L label

--label=label

Use label instead of the file name in the context format (see Context Format) and unified format (see Unified Format) headers. See RCS Scripts.

--left-column

Print only the left column of two common lines in side by side format. See Controlling Side by Side Format.

--line-format=format

Use format to output all input lines in if-then-else format. See Line Formats.

-n

--rcs

Output RCS-format diffs; like -f except that each command specifies the number of lines affected. See RCS Scripts.

-N

--new-file

If one file is missing, treat it as present but empty. See Comparing Directories.

--new-group-format=format

Use format to output a group of lines taken from just the second file in if-then-else format. See Line Group Formats.

--new-line-format=format

Use format to output a line taken from just the second file in if-then-else format. See Line Formats.

--no-dereference

Act on symbolic links themselves instead of what they point to. Two symbolic links are deemed equal only when each points to precisely the same name.

--old-group-format=format

Use format to output a group of lines taken from just the first file in if-then-else format. See Line Group Formats.

--old-line-format=format

Use format to output a line taken from just the first file in if-then-else format. See Line Formats.

-p

--show-c-function

Show which C function each change is in. See Showing C Function Headings.

--palette=palette

Specify what color palette to use when colored output is enabled. It defaults to ‘rs=0:hd=1:ad=32:de=31:ln=36’ for red deleted lines, green added lines, cyan line numbers, bold header.

Supported capabilities are as follows.

ad=32 ¶

SGR substring for added lines. The default is green foreground.

de=31 ¶

SGR substring for deleted lines. The default is red foreground.

hd=1 ¶

SGR substring for chunk header. The default is bold foreground.

ln=36 ¶

SGR substring for line numbers. The default is cyan foreground.

-q

--brief

Report only whether the files differ, not the details of the differences. See Summarizing Which Files Differ.

-r

--recursive

When comparing directories, recursively compare any subdirectories found. See Comparing Directories.

-s

--report-identical-files

Report when two files are the same. See Comparing Directories.

-S file

--starting-file=file

When comparing directories, start with the file file. This is used for resuming an aborted comparison. See Comparing Directories.

--speed-large-files

Use heuristics to speed handling of large files that have numerous scattered small changes. See diff Performance Tradeoffs.

--strip-trailing-cr

Strip any trailing carriage return at the end of an input line. See Binary Files and Forcing Text Comparisons.

--suppress-common-lines

Do not print common lines in side by side format. See Controlling Side by Side Format.

-t

--expand-tabs

Expand tabs to spaces in the output, to preserve the alignment of tabs in the input files. See Preserving Tab Stop Alignment.

-T

--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. See Preserving Tab Stop Alignment.

--tabsize=columns

Assume that tab stops are set every columns (default 8) print columns. See Preserving Tab Stop Alignment.

--suppress-blank-empty

Suppress any blanks before newlines when printing the representation of an empty line, when outputting normal, context, or unified format. See Omitting trailing blanks.

--to-file=file

Compare each operand to file; file may be a directory.

-u

Use the unified output format, showing three lines of context. See Unified Format.

--unchanged-group-format=format

Use format to output a group of common lines taken from both files in if-then-else format. See Line Group Formats.

--unchanged-line-format=format

Use format to output a line common to both files in if-then-else format. See Line Formats.

--unidirectional-new-file

If a first file is missing, treat it as present but empty. See Comparing Directories.

-U lines

--unified[=lines]

Use the unified output format, showing lines (an integer) lines of context, or three if lines is not given. See Unified Format. For proper operation, patch typically needs at least two lines of context.

On older systems, diff supports an obsolete option -lines that has effect when combined with -u. POSIX 1003.1-2001 (see Standards conformance) does not allow this; use -U lines instead.

-v

--version

Output version information and then exit.

-w

--ignore-all-space

Ignore white space when comparing lines. See Suppressing Differences in Blank and Tab Spacing.

-W columns

--width=columns

Output at most columns (default 130) print columns per line in side by side format. See Controlling Side by Side Format.

-x pattern

--exclude=pattern

When comparing directories, ignore files and subdirectories whose basenames match pattern. See Comparing Directories.

-X file

--exclude-from=file

When comparing directories, ignore files and subdirectories whose basenames match any pattern contained in file. See Comparing Directories.

-y

--side-by-side

Use the side by side output format. See Controlling Side by Side Format.

-Z

--ignore-trailing-space

Ignore white space at line end. See Suppressing Differences in Blank and Tab Spacing.