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<a name="Invoking-diff"></a>
<div class="header">
<p>
Next: <a href="Invoking-diff3.html#Invoking-diff3" accesskey="n" rel="next">Invoking diff3</a>, Previous: <a href="Invoking-cmp.html#Invoking-cmp" accesskey="p" rel="prev">Invoking cmp</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Invoking-diff-1"></a>
<h2 class="chapter">13 Invoking <code>diff</code></h2>
<a name="index-invoking-diff"></a>
<a name="index-diff-invocation"></a>

<p>The format for running the <code>diff</code> command is:
</p>
<div class="example">
<pre class="example">diff <var>options</var>&hellip; <var>files</var>&hellip;
</pre></div>

<p>In the simplest case, two file names <var>from-file</var> and
<var>to-file</var> are given, and <code>diff</code> compares the contents of
<var>from-file</var> and <var>to-file</var>.  A file name of <samp>-</samp> stands for
the standard input.
</p>
<p>If one file is a directory and the other is not, <code>diff</code> compares
the file in the directory whose name is that of the non-directory.
The non-directory file must not be <samp>-</samp>.
</p>
<p>If two file names are given and both are directories,
<code>diff</code> compares corresponding files in both directories, in
alphabetical order; this comparison is not recursive unless the
<samp>--recursive</samp> (<samp>-r</samp>) option is given.  <code>diff</code> 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 &ldquo;file with the same name&rdquo; does not
apply.
</p>
<p>If the <samp>--from-file=<var>file</var></samp> option is given, the number of
file names is arbitrary, and <var>file</var> is compared to each named file.
Similarly, if the <samp>--to-file=<var>file</var></samp> option is given, each
named file is compared to <var>file</var>.
</p>
<p><code>diff</code> options begin with &lsquo;<samp>-</samp>&rsquo;, so normally file names
may not begin with &lsquo;<samp>-</samp>&rsquo;.  However, <samp>--</samp> as an
argument by itself treats the remaining arguments as file names even if
they begin with &lsquo;<samp>-</samp>&rsquo;.
</p>
<p>An exit status of 0 means no differences were found, 1 means some
differences were found, and 2 means trouble.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#diff-Options" accesskey="1">diff Options</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Summary of options to <code>diff</code>.
</td></tr>
</table>

<hr>
<a name="diff-Options"></a>
<div class="header">
<p>
Up: <a href="#Invoking-diff" accesskey="u" rel="up">Invoking diff</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Options-to-diff"></a>
<h3 class="section">13.1 Options to <code>diff</code></h3>
<a name="index-diff-options"></a>
<a name="index-options-for-diff"></a>

<p>Below is a summary of all of the options that <acronym>GNU</acronym>
<code>diff</code> accepts.  Most options have two equivalent names, one
of which is a single letter preceded by &lsquo;<samp>-</samp>&rsquo;, and the other of
which is a long name preceded by &lsquo;<samp>--</samp>&rsquo;.  Multiple single letter
options (unless they take an argument) can be combined into a single
command line word: <samp>-ac</samp> is equivalent to <samp>-a -c</samp>.  Long
named options can be abbreviated to any unique prefix of their name.
Brackets ([ and ]) indicate that an option takes an optional argument.
</p>
<dl compact="compact">
<dt><samp>-a</samp></dt>
<dt><samp>--text</samp></dt>
<dd><p>Treat all files as text and compare them line-by-line, even if they
do not seem to be text.  See <a href="Comparison.html#Binary">Binary</a>.
</p>
</dd>
<dt><samp>-b</samp></dt>
<dt><samp>--ignore-space-change</samp></dt>
<dd><p>Ignore changes in amount of white space.  See <a href="Comparison.html#White-Space">White Space</a>.
</p>
</dd>
<dt><samp>-B</samp></dt>
<dt><samp>--ignore-blank-lines</samp></dt>
<dd><p>Ignore changes that just insert or delete blank lines.  See <a href="Comparison.html#Blank-Lines">Blank Lines</a>.
</p>
</dd>
<dt><samp>--binary</samp></dt>
<dd><p>Read and write data in binary mode.  See <a href="Comparison.html#Binary">Binary</a>.
</p>
</dd>
<dt><samp>-c</samp></dt>
<dd><p>Use the context output format, showing three lines of context.
See <a href="Output-Formats.html#Context-Format">Context Format</a>.
</p>
</dd>
<dt><samp>--color [=<var>when</var>]</samp></dt>
<dd><a name="index-color_002c-distinguishing-different-context"></a>
<p>Specify whether to use color for distinguishing different contexts,
like header, added or removed lines.  <var>when</var> may be omitted, or
one of:
</p><ul>
<li> none
<a name="index-none-color-option"></a>
Do not use color at all.  This is the default when no &ndash;color option
is specified.
</li><li> auto
<a name="index-auto-color-option"></a>
<a name="index-terminal_002c-using-color-iff"></a>
Use color only if standard output is a terminal.
</li><li> always
<a name="index-always-color-option"></a>
Always use color.
</li></ul>
<p>Specifying <samp>--color</samp> and no <var>when</var> is equivalent to
<samp>--color=auto</samp>.
</p>
</dd>
<dt><samp>-C <var>lines</var></samp></dt>
<dt><samp>--context<span class="roman">[</span>=<var>lines</var><span class="roman">]</span></samp></dt>
<dd><p>Use the context output format, showing <var>lines</var> (an integer) lines of
context, or three if <var>lines</var> is not given.  See <a href="Output-Formats.html#Context-Format">Context Format</a>.
For proper operation, <code>patch</code> typically needs at least two lines of
context.
</p>
<p>For compatibility <code>diff</code> also supports an obsolete option
syntax <samp>-<var>lines</var></samp> that has effect when combined with
<samp>-c</samp>, <samp>-p</samp>, or <samp>-u</samp>.  New scripts should use
<samp>-U <var>lines</var></samp> (<samp>-C <var>lines</var></samp>) instead.
</p>
</dd>
<dt><samp>--changed-group-format=<var>format</var></samp></dt>
<dd><p>Use <var>format</var> to output a line group containing differing lines from
both files in if-then-else format.  See <a href="Output-Formats.html#Line-Group-Formats">Line Group Formats</a>.
</p>
</dd>
<dt><samp>-d</samp></dt>
<dt><samp>--minimal</samp></dt>
<dd><p>Change the algorithm perhaps find a smaller set of changes.  This makes
<code>diff</code> slower (sometimes much slower).  See <a href="diff-Performance.html#diff-Performance">diff Performance</a>.
</p>
</dd>
<dt><samp>-D <var>name</var></samp></dt>
<dt><samp>--ifdef=<var>name</var></samp></dt>
<dd><p>Make merged &lsquo;<samp>#ifdef</samp>&rsquo; format output, conditional on the preprocessor
macro <var>name</var>.  See <a href="Output-Formats.html#If_002dthen_002delse">If-then-else</a>.
</p>
</dd>
<dt><samp>-e</samp></dt>
<dt><samp>--ed</samp></dt>
<dd><p>Make output that is a valid <code>ed</code> script.  See <a href="Output-Formats.html#ed-Scripts">ed Scripts</a>.
</p>
</dd>
<dt><samp>-E</samp></dt>
<dt><samp>--ignore-tab-expansion</samp></dt>
<dd><p>Ignore changes due to tab expansion.
See <a href="Comparison.html#White-Space">White Space</a>.
</p>
</dd>
<dt><samp>-f</samp></dt>
<dt><samp>--forward-ed</samp></dt>
<dd><p>Make output that looks vaguely like an <code>ed</code> script but has changes
in the order they appear in the file.  See <a href="Output-Formats.html#Forward-ed">Forward ed</a>.
</p>
</dd>
<dt><samp>-F <var>regexp</var></samp></dt>
<dt><samp>--show-function-line=<var>regexp</var></samp></dt>
<dd><p>In context and unified format, for each hunk of differences, show some
of the last preceding line that matches <var>regexp</var>.  See <a href="Output-Formats.html#Specified-Headings">Specified Headings</a>.
</p>
</dd>
<dt><samp>--from-file=<var>file</var></samp></dt>
<dd><p>Compare <var>file</var> to each operand; <var>file</var> may be a directory.
</p>
</dd>
<dt><samp>--help</samp></dt>
<dd><p>Output a summary of usage and then exit.
</p>
</dd>
<dt><samp>--horizon-lines=<var>lines</var></samp></dt>
<dd><p>Do not discard the last <var>lines</var> lines of the common prefix
and the first <var>lines</var> lines of the common suffix.
See <a href="diff-Performance.html#diff-Performance">diff Performance</a>.
</p>
</dd>
<dt><samp>-i</samp></dt>
<dt><samp>--ignore-case</samp></dt>
<dd><p>Ignore changes in case; consider upper- and lower-case letters
equivalent.  See <a href="Comparison.html#Case-Folding">Case Folding</a>.
</p>
</dd>
<dt><samp>-I <var>regexp</var></samp></dt>
<dt><samp>--ignore-matching-lines=<var>regexp</var></samp></dt>
<dd><p>Ignore changes that just insert or delete lines that match <var>regexp</var>.
See <a href="Comparison.html#Specified-Lines">Specified Lines</a>.
</p>
</dd>
<dt><samp>--ignore-file-name-case</samp></dt>
<dd><p>Ignore case when comparing file names.  For example, recursive
comparison of <samp>d</samp> to <samp>e</samp> might compare the contents of
<samp>d/Init</samp> and <samp>e/inIt</samp>.  At the top level, &lsquo;<samp>diff d inIt</samp>&rsquo;
might compare the contents of <samp>d/Init</samp> and <samp>inIt</samp>.
See <a href="Comparing-Directories.html#Comparing-Directories">Comparing Directories</a>.
</p>
</dd>
<dt><samp>-l</samp></dt>
<dt><samp>--paginate</samp></dt>
<dd><p>Pass the output through <code>pr</code> to paginate it.  See <a href="Adjusting-Output.html#Pagination">Pagination</a>.
</p>
</dd>
<dt><samp>-L <var>label</var></samp></dt>
<dt><samp>--label=<var>label</var></samp></dt>
<dd><p>Use <var>label</var> instead of the file name in the context format
(see <a href="Output-Formats.html#Context-Format">Context Format</a>) and unified format (see <a href="Output-Formats.html#Unified-Format">Unified Format</a>)
headers.  See <a href="Output-Formats.html#RCS">RCS</a>.
</p>
</dd>
<dt><samp>--left-column</samp></dt>
<dd><p>Print only the left column of two common lines in side by side format.
See <a href="Output-Formats.html#Side-by-Side-Format">Side by Side Format</a>.
</p>
</dd>
<dt><samp>--line-format=<var>format</var></samp></dt>
<dd><p>Use <var>format</var> to output all input lines in if-then-else format.
See <a href="Output-Formats.html#Line-Formats">Line Formats</a>.
</p>
</dd>
<dt><samp>-n</samp></dt>
<dt><samp>--rcs</samp></dt>
<dd><p>Output <acronym>RCS</acronym>-format diffs; like <samp>-f</samp> except that each command
specifies the number of lines affected.  See <a href="Output-Formats.html#RCS">RCS</a>.
</p>
</dd>
<dt><samp>-N</samp></dt>
<dt><samp>--new-file</samp></dt>
<dd><p>If one file is missing, treat it as present but empty.
See <a href="Comparing-Directories.html#Comparing-Directories">Comparing Directories</a>.
</p>
</dd>
<dt><samp>--new-group-format=<var>format</var></samp></dt>
<dd><p>Use <var>format</var> to output a group of lines taken from just the second
file in if-then-else format.  See <a href="Output-Formats.html#Line-Group-Formats">Line Group Formats</a>.
</p>
</dd>
<dt><samp>--new-line-format=<var>format</var></samp></dt>
<dd><p>Use <var>format</var> to output a line taken from just the second file in
if-then-else format.  See <a href="Output-Formats.html#Line-Formats">Line Formats</a>.
</p>
</dd>
<dt><samp>--no-dereference</samp></dt>
<dd><p>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.
</p>
</dd>
<dt><samp>--old-group-format=<var>format</var></samp></dt>
<dd><p>Use <var>format</var> to output a group of lines taken from just the first
file in if-then-else format.  See <a href="Output-Formats.html#Line-Group-Formats">Line Group Formats</a>.
</p>
</dd>
<dt><samp>--old-line-format=<var>format</var></samp></dt>
<dd><p>Use <var>format</var> to output a line taken from just the first file in
if-then-else format.  See <a href="Output-Formats.html#Line-Formats">Line Formats</a>.
</p>
</dd>
<dt><samp>-p</samp></dt>
<dt><samp>--show-c-function</samp></dt>
<dd><p>Show which C function each change is in.  See <a href="Output-Formats.html#C-Function-Headings">C Function Headings</a>.
</p>
</dd>
<dt><samp>--palette=<var>palette</var></samp></dt>
<dd><p>Specify what color palette to use when colored output is enabled.  It
defaults to &lsquo;<samp>rs=0:hd=1:ad=32:de=31:ln=36</samp>&rsquo; for red deleted lines,
green added lines, cyan line numbers, bold header.
</p>
<p>Supported capabilities are as follows.
</p>
<dl compact="compact">
<dt><code>ad=32</code></dt>
<dd><a name="index-ad-capability"></a>

<p>SGR substring for added lines.
The default is green foreground.
</p>
</dd>
<dt><code>de=31</code></dt>
<dd><a name="index-de-capability"></a>

<p>SGR substring for deleted lines.
The default is red foreground.
</p>
</dd>
<dt><code>hd=1</code></dt>
<dd><a name="index-hd-capability"></a>

<p>SGR substring for chunk header.
The default is bold foreground.
</p>
</dd>
<dt><code>ln=36</code></dt>
<dd><a name="index-ln-capability"></a>

<p>SGR substring for line numbers.
The default is cyan foreground.
</p></dd>
</dl>


</dd>
<dt><samp>-q</samp></dt>
<dt><samp>--brief</samp></dt>
<dd><p>Report only whether the files differ, not the details of the
differences.  See <a href="Comparison.html#Brief">Brief</a>.
</p>
</dd>
<dt><samp>-r</samp></dt>
<dt><samp>--recursive</samp></dt>
<dd><p>When comparing directories, recursively compare any subdirectories
found.  See <a href="Comparing-Directories.html#Comparing-Directories">Comparing Directories</a>.
</p>
</dd>
<dt><samp>-s</samp></dt>
<dt><samp>--report-identical-files</samp></dt>
<dd><p>Report when two files are the same.  See <a href="Comparing-Directories.html#Comparing-Directories">Comparing Directories</a>.
</p>
</dd>
<dt><samp>-S <var>file</var></samp></dt>
<dt><samp>--starting-file=<var>file</var></samp></dt>
<dd><p>When comparing directories, start with the file <var>file</var>.  This is
used for resuming an aborted comparison.  See <a href="Comparing-Directories.html#Comparing-Directories">Comparing Directories</a>.
</p>
</dd>
<dt><samp>--speed-large-files</samp></dt>
<dd><p>Use heuristics to speed handling of large files that have numerous
scattered small changes.  See <a href="diff-Performance.html#diff-Performance">diff Performance</a>.
</p>
</dd>
<dt><samp>--strip-trailing-cr</samp></dt>
<dd><p>Strip any trailing carriage return at the end of an input line.
See <a href="Comparison.html#Binary">Binary</a>.
</p>
</dd>
<dt><samp>--suppress-common-lines</samp></dt>
<dd><p>Do not print common lines in side by side format.
See <a href="Output-Formats.html#Side-by-Side-Format">Side by Side Format</a>.
</p>
</dd>
<dt><samp>-t</samp></dt>
<dt><samp>--expand-tabs</samp></dt>
<dd><p>Expand tabs to spaces in the output, to preserve the alignment of tabs
in the input files.  See <a href="Adjusting-Output.html#Tabs">Tabs</a>.
</p>
</dd>
<dt><samp>-T</samp></dt>
<dt><samp>--initial-tab</samp></dt>
<dd><p>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 <a href="Adjusting-Output.html#Tabs">Tabs</a>.
</p>
</dd>
<dt><samp>--tabsize=<var>columns</var></samp></dt>
<dd><p>Assume that tab stops are set every <var>columns</var> (default 8) print
columns.  See <a href="Adjusting-Output.html#Tabs">Tabs</a>.
</p>
</dd>
<dt><samp>--suppress-blank-empty</samp></dt>
<dd><p>Suppress any blanks before newlines when printing the representation
of an empty line, when outputting normal, context, or unified format.
See <a href="Adjusting-Output.html#Trailing-Blanks">Trailing Blanks</a>.
</p>
</dd>
<dt><samp>--to-file=<var>file</var></samp></dt>
<dd><p>Compare each operand to <var>file</var>; <var>file</var> may be a directory.
</p>
</dd>
<dt><samp>-u</samp></dt>
<dd><p>Use the unified output format, showing three lines of context.
See <a href="Output-Formats.html#Unified-Format">Unified Format</a>.
</p>
</dd>
<dt><samp>--unchanged-group-format=<var>format</var></samp></dt>
<dd><p>Use <var>format</var> to output a group of common lines taken from both files
in if-then-else format.  See <a href="Output-Formats.html#Line-Group-Formats">Line Group Formats</a>.
</p>
</dd>
<dt><samp>--unchanged-line-format=<var>format</var></samp></dt>
<dd><p>Use <var>format</var> to output a line common to both files in if-then-else
format.  See <a href="Output-Formats.html#Line-Formats">Line Formats</a>.
</p>
</dd>
<dt><samp>--unidirectional-new-file</samp></dt>
<dd><p>If a first file is missing, treat it as present but empty.
See <a href="Comparing-Directories.html#Comparing-Directories">Comparing Directories</a>.
</p>
</dd>
<dt><samp>-U <var>lines</var></samp></dt>
<dt><samp>--unified<span class="roman">[</span>=<var>lines</var><span class="roman">]</span></samp></dt>
<dd><p>Use the unified output format, showing <var>lines</var> (an integer) lines of
context, or three if <var>lines</var> is not given.  See <a href="Output-Formats.html#Unified-Format">Unified Format</a>.
For proper operation, <code>patch</code> typically needs at least two lines of
context.
</p>
<p>On older systems, <code>diff</code> supports an obsolete option
<samp>-<var>lines</var></samp> that has effect when combined with <samp>-u</samp>.
<acronym>POSIX</acronym> 1003.1-2001 (see <a href="Standards-conformance.html#Standards-conformance">Standards conformance</a>) does not allow
this; use <samp>-U <var>lines</var></samp> instead.
</p>
</dd>
<dt><samp>-v</samp></dt>
<dt><samp>--version</samp></dt>
<dd><p>Output version information and then exit.
</p>
</dd>
<dt><samp>-w</samp></dt>
<dt><samp>--ignore-all-space</samp></dt>
<dd><p>Ignore white space when comparing lines.  See <a href="Comparison.html#White-Space">White Space</a>.
</p>
</dd>
<dt><samp>-W <var>columns</var></samp></dt>
<dt><samp>--width=<var>columns</var></samp></dt>
<dd><p>Output at most <var>columns</var> (default 130) print columns per line in
side by side format.  See <a href="Output-Formats.html#Side-by-Side-Format">Side by Side Format</a>.
</p>
</dd>
<dt><samp>-x <var>pattern</var></samp></dt>
<dt><samp>--exclude=<var>pattern</var></samp></dt>
<dd><p>When comparing directories, ignore files and subdirectories whose basenames
match <var>pattern</var>.  See <a href="Comparing-Directories.html#Comparing-Directories">Comparing Directories</a>.
</p>
</dd>
<dt><samp>-X <var>file</var></samp></dt>
<dt><samp>--exclude-from=<var>file</var></samp></dt>
<dd><p>When comparing directories, ignore files and subdirectories whose basenames
match any pattern contained in <var>file</var>.  See <a href="Comparing-Directories.html#Comparing-Directories">Comparing Directories</a>.
</p>
</dd>
<dt><samp>-y</samp></dt>
<dt><samp>--side-by-side</samp></dt>
<dd><p>Use the side by side output format.  See <a href="Output-Formats.html#Side-by-Side-Format">Side by Side Format</a>.
</p>
</dd>
<dt><samp>-Z</samp></dt>
<dt><samp>--ignore-trailing-space</samp></dt>
<dd><p>Ignore white space at line end.  See <a href="Comparison.html#White-Space">White Space</a>.
</p></dd>
</dl>

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