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 <a name="Environment-Variables"></a>
 <div class="header">
 <p>
 Next: <a href="Precompiled-Headers.html#Precompiled-Headers" accesskey="n" rel="next">Precompiled Headers</a>, Previous: <a href="Code-Gen-Options.html#Code-Gen-Options" accesskey="p" rel="prev">Code Gen Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
 </div>
 <hr>
 <a name="Environment-Variables-Affecting-GCC"></a>
 <h3 class="section">3.19 Environment Variables Affecting GCC</h3>
 <a name="index-environment-variables"></a>

 <p>This section describes several environment variables that affect how GCC
 operates.  Some of them work by specifying directories or prefixes to use
 when searching for various kinds of files.  Some are used to specify other
 aspects of the compilation environment.
 </p>
 <p>Note that you can also specify places to search using options such as
 <samp>-B</samp>, <samp>-I</samp> and <samp>-L</samp> (see <a href="Directory-Options.html#Directory-Options">Directory Options</a>).  These
 take precedence over places specified using environment variables, which
 in turn take precedence over those specified by the configuration of GCC.
 See <a href="http://gcc.gnu.org/onlinedocs/gccint/Driver.html#Driver">Controlling the Compilation Driver <samp>gcc</samp></a> in <cite>GNU Compiler Collection (GCC) Internals</cite>.
 </p>
 <dl compact="compact">
 <dt><code>LANG</code></dt>
 <dt><code>LC_CTYPE</code></dt>
 <dt><code>LC_MESSAGES</code></dt>
 <dt><code>LC_ALL</code></dt>
 <dd><a name="index-LANG"></a>
 <a name="index-LC_005fCTYPE"></a>
 <a name="index-LC_005fMESSAGES"></a>
 <a name="index-LC_005fALL"></a>
 <a name="index-locale"></a>
 <p>These environment variables control the way that GCC uses
 localization information which allows GCC to work with different
 national conventions.  GCC inspects the locale categories
 <code>LC_CTYPE</code> and <code>LC_MESSAGES</code> if it has been configured to do
 so.  These locale categories can be set to any value supported by your
 installation.  A typical value is &lsquo;<samp>en_GB.UTF-8</samp>&rsquo; for English in the United
 Kingdom encoded in UTF-8.
 </p>
 <p>The <code>LC_CTYPE</code> environment variable specifies character
 classification.  GCC uses it to determine the character boundaries in
 a string; this is needed for some multibyte encodings that contain quote
 and escape characters that are otherwise interpreted as a string
 end or escape.
 </p>
 <p>The <code>LC_MESSAGES</code> environment variable specifies the language to
 use in diagnostic messages.
 </p>
 <p>If the <code>LC_ALL</code> environment variable is set, it overrides the value
 of <code>LC_CTYPE</code> and <code>LC_MESSAGES</code>; otherwise, <code>LC_CTYPE</code>
 and <code>LC_MESSAGES</code> default to the value of the <code>LANG</code>
 environment variable.  If none of these variables are set, GCC
 defaults to traditional C English behavior.
 </p>
 </dd>
 <dt><code>TMPDIR</code></dt>
 <dd><a name="index-TMPDIR"></a>
 <p>If <code>TMPDIR</code> is set, it specifies the directory to use for temporary
 files.  GCC uses temporary files to hold the output of one stage of
 compilation which is to be used as input to the next stage: for example,
 the output of the preprocessor, which is the input to the compiler
 proper.
 </p>
 </dd>
 <dt><code>GCC_COMPARE_DEBUG</code></dt>
 <dd><a name="index-GCC_005fCOMPARE_005fDEBUG"></a>
 <p>Setting <code>GCC_COMPARE_DEBUG</code> is nearly equivalent to passing
 <samp>-fcompare-debug</samp> to the compiler driver.  See the documentation
 of this option for more details.
 </p>
 </dd>
 <dt><code>GCC_EXEC_PREFIX</code></dt>
 <dd><a name="index-GCC_005fEXEC_005fPREFIX"></a>
 <p>If <code>GCC_EXEC_PREFIX</code> is set, it specifies a prefix to use in the
 names of the subprograms executed by the compiler.  No slash is added
 when this prefix is combined with the name of a subprogram, but you can
 specify a prefix that ends with a slash if you wish.
 </p>
 <p>If <code>GCC_EXEC_PREFIX</code> is not set, GCC attempts to figure out
 an appropriate prefix to use based on the pathname it is invoked with.
 </p>
 <p>If GCC cannot find the subprogram using the specified prefix, it
 tries looking in the usual places for the subprogram.
 </p>
 <p>The default value of <code>GCC_EXEC_PREFIX</code> is
 <samp><var>prefix</var>/lib/gcc/</samp> where <var>prefix</var> is the prefix to
 the installed compiler. In many cases <var>prefix</var> is the value
 of <code>prefix</code> when you ran the <samp>configure</samp> script.
 </p>
 <p>Other prefixes specified with <samp>-B</samp> take precedence over this prefix.
 </p>
 <p>This prefix is also used for finding files such as <samp>crt0.o</samp> that are
 used for linking.
 </p>
 <p>In addition, the prefix is used in an unusual way in finding the
 directories to search for header files.  For each of the standard
 directories whose name normally begins with &lsquo;<samp>/usr/local/lib/gcc</samp>&rsquo;
 (more precisely, with the value of <code>GCC_INCLUDE_DIR</code>), GCC tries
 replacing that beginning with the specified prefix to produce an
 alternate directory name.  Thus, with <samp>-Bfoo/</samp>, GCC searches
 <samp>foo/bar</samp> just before it searches the standard directory
 <samp>/usr/local/lib/bar</samp>.
 If a standard directory begins with the configured
 <var>prefix</var> then the value of <var>prefix</var> is replaced by
 <code>GCC_EXEC_PREFIX</code> when looking for header files.
 </p>
 </dd>
 <dt><code>COMPILER_PATH</code></dt>
 <dd><a name="index-COMPILER_005fPATH"></a>
 <p>The value of <code>COMPILER_PATH</code> is a colon-separated list of
 directories, much like <code>PATH</code>.  GCC tries the directories thus
 specified when searching for subprograms, if it can&rsquo;t find the
 subprograms using <code>GCC_EXEC_PREFIX</code>.
 </p>
 </dd>
 <dt><code>LIBRARY_PATH</code></dt>
 <dd><a name="index-LIBRARY_005fPATH"></a>
 <p>The value of <code>LIBRARY_PATH</code> is a colon-separated list of
 directories, much like <code>PATH</code>.  When configured as a native compiler,
 GCC tries the directories thus specified when searching for special
 linker files, if it can&rsquo;t find them using <code>GCC_EXEC_PREFIX</code>.  Linking
 using GCC also uses these directories when searching for ordinary
 libraries for the <samp>-l</samp> option (but directories specified with
 <samp>-L</samp> come first).
 </p>
 </dd>
 <dt><code>LANG</code></dt>
 <dd><a name="index-LANG-1"></a>
 <a name="index-locale-definition"></a>
 <p>This variable is used to pass locale information to the compiler.  One way in
 which this information is used is to determine the character set to be used
 when character literals, string literals and comments are parsed in C and C++.
 When the compiler is configured to allow multibyte characters,
 the following values for <code>LANG</code> are recognized:
 </p>
 <dl compact="compact">
 <dt>&lsquo;<samp>C-JIS</samp>&rsquo;</dt>
 <dd><p>Recognize JIS characters.
 </p></dd>
 <dt>&lsquo;<samp>C-SJIS</samp>&rsquo;</dt>
 <dd><p>Recognize SJIS characters.
 </p></dd>
 <dt>&lsquo;<samp>C-EUCJP</samp>&rsquo;</dt>
 <dd><p>Recognize EUCJP characters.
 </p></dd>
 </dl>

 <p>If <code>LANG</code> is not defined, or if it has some other value, then the
 compiler uses <code>mblen</code> and <code>mbtowc</code> as defined by the default locale to
 recognize and translate multibyte characters.
 </p></dd>
 </dl>

 <p>Some additional environment variables affect the behavior of the
 preprocessor.
 </p>


 <dl compact="compact">
 <dt><code>CPATH</code>
 <a name="index-CPATH"></a>
 </dt>
 <dt><code>C_INCLUDE_PATH</code>
 <a name="index-C_005fINCLUDE_005fPATH"></a>
 </dt>
 <dt><code>CPLUS_INCLUDE_PATH</code>
 <a name="index-CPLUS_005fINCLUDE_005fPATH"></a>
 </dt>
 <dt><code>OBJC_INCLUDE_PATH</code>
 <a name="index-OBJC_005fINCLUDE_005fPATH"></a>
 </dt>
 <dd><p>Each variable&rsquo;s value is a list of directories separated by a special
 character, much like <code>PATH</code>, in which to look for header files.
 The special character, <code>PATH_SEPARATOR</code>, is target-dependent and
 determined at GCC build time.  For Microsoft Windows-based targets it is a
 semicolon, and for almost all other targets it is a colon.
 </p>
 <p><code>CPATH</code> specifies a list of directories to be searched as if
 specified with <samp>-I</samp>, but after any paths given with <samp>-I</samp>
 options on the command line.  This environment variable is used
 regardless of which language is being preprocessed.
 </p>
 <p>The remaining environment variables apply only when preprocessing the
 particular language indicated.  Each specifies a list of directories
 to be searched as if specified with <samp>-isystem</samp>, but after any
 paths given with <samp>-isystem</samp> options on the command line.
 </p>
 <p>In all these variables, an empty element instructs the compiler to
 search its current working directory.  Empty elements can appear at the
 beginning or end of a path.  For instance, if the value of
 <code>CPATH</code> is <code>:/special/include</code>, that has the same
 effect as &lsquo;<samp><span class="nolinebreak">-I.</span>&nbsp;<span class="nolinebreak">-I/special/include</span><!-- /@w --></samp>&rsquo;.
 </p>

 </dd>
 <dt><code>DEPENDENCIES_OUTPUT</code>
 <a name="index-DEPENDENCIES_005fOUTPUT"></a>
 </dt>
 <dd><a name="index-dependencies-for-make-as-output"></a>
 <p>If this variable is set, its value specifies how to output
 dependencies for Make based on the non-system header files processed
 by the compiler.  System header files are ignored in the dependency
 output.
 </p>
 <p>The value of <code>DEPENDENCIES_OUTPUT</code> can be just a file name, in
 which case the Make rules are written to that file, guessing the target
 name from the source file name.  Or the value can have the form
 &lsquo;<samp><var>file</var> <var>target</var></samp>&rsquo;, in which case the rules are written to
 file <var>file</var> using <var>target</var> as the target name.
 </p>
 <p>In other words, this environment variable is equivalent to combining
 the options <samp>-MM</samp> and <samp>-MF</samp>
 (see <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>),
 with an optional <samp>-MT</samp> switch too.
 </p>
 </dd>
 <dt><code>SUNPRO_DEPENDENCIES</code>
 <a name="index-SUNPRO_005fDEPENDENCIES"></a>
 </dt>
 <dd><a name="index-dependencies-for-make-as-output-1"></a>
 <p>This variable is the same as <code>DEPENDENCIES_OUTPUT</code> (see above),
 except that system header files are not ignored, so it implies
 <samp>-M</samp> rather than <samp>-MM</samp>.  However, the dependence on the
 main input file is omitted.
 See <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>.
 </p></dd>
 </dl>


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	<a name="Environment-Variables"></a>
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	<p>
	Next: <a href="Precompiled-Headers.html#Precompiled-Headers" accesskey="n" rel="next">Precompiled Headers</a>, Previous: <a href="Code-Gen-Options.html#Code-Gen-Options" accesskey="p" rel="prev">Code Gen Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
	</div>
	<hr>
	<a name="Environment-Variables-Affecting-GCC"></a>
	<h3 class="section">3.19 Environment Variables Affecting GCC</h3>
	<a name="index-environment-variables"></a>

	<p>This section describes several environment variables that affect how GCC
	operates. Some of them work by specifying directories or prefixes to use
	when searching for various kinds of files. Some are used to specify other
	aspects of the compilation environment.
	</p>
	<p>Note that you can also specify places to search using options such as
	<samp>-B</samp>, <samp>-I</samp> and <samp>-L</samp> (see <a href="Directory-Options.html#Directory-Options">Directory Options</a>). These
	take precedence over places specified using environment variables, which
	in turn take precedence over those specified by the configuration of GCC.
	See <a href="http://gcc.gnu.org/onlinedocs/gccint/Driver.html#Driver">Controlling the Compilation Driver <samp>gcc</samp></a> in <cite>GNU Compiler Collection (GCC) Internals</cite>.
	</p>
	<dl compact="compact">
	<dt><code>LANG</code></dt>
	<dt><code>LC_CTYPE</code></dt>
	<dt><code>LC_MESSAGES</code></dt>
	<dt><code>LC_ALL</code></dt>
	<dd><a name="index-LANG"></a>
	<a name="index-LC_005fCTYPE"></a>
	<a name="index-LC_005fMESSAGES"></a>
	<a name="index-LC_005fALL"></a>
	<a name="index-locale"></a>
	<p>These environment variables control the way that GCC uses
	localization information which allows GCC to work with different
	national conventions. GCC inspects the locale categories
	<code>LC_CTYPE</code> and <code>LC_MESSAGES</code> if it has been configured to do
	so. These locale categories can be set to any value supported by your
	installation. A typical value is ‘<samp>en_GB.UTF-8</samp>’ for English in the United
	Kingdom encoded in UTF-8.
	</p>
	<p>The <code>LC_CTYPE</code> environment variable specifies character
	classification. GCC uses it to determine the character boundaries in
	a string; this is needed for some multibyte encodings that contain quote
	and escape characters that are otherwise interpreted as a string
	end or escape.
	</p>
	<p>The <code>LC_MESSAGES</code> environment variable specifies the language to
	use in diagnostic messages.
	</p>
	<p>If the <code>LC_ALL</code> environment variable is set, it overrides the value
	of <code>LC_CTYPE</code> and <code>LC_MESSAGES</code>; otherwise, <code>LC_CTYPE</code>
	and <code>LC_MESSAGES</code> default to the value of the <code>LANG</code>
	environment variable. If none of these variables are set, GCC
	defaults to traditional C English behavior.
	</p>
	</dd>
	<dt><code>TMPDIR</code></dt>
	<dd><a name="index-TMPDIR"></a>
	<p>If <code>TMPDIR</code> is set, it specifies the directory to use for temporary
	files. GCC uses temporary files to hold the output of one stage of
	compilation which is to be used as input to the next stage: for example,
	the output of the preprocessor, which is the input to the compiler
	proper.
	</p>
	</dd>
	<dt><code>GCC_COMPARE_DEBUG</code></dt>
	<dd><a name="index-GCC_005fCOMPARE_005fDEBUG"></a>
	<p>Setting <code>GCC_COMPARE_DEBUG</code> is nearly equivalent to passing
	<samp>-fcompare-debug</samp> to the compiler driver. See the documentation
	of this option for more details.
	</p>
	</dd>
	<dt><code>GCC_EXEC_PREFIX</code></dt>
	<dd><a name="index-GCC_005fEXEC_005fPREFIX"></a>
	<p>If <code>GCC_EXEC_PREFIX</code> is set, it specifies a prefix to use in the
	names of the subprograms executed by the compiler. No slash is added
	when this prefix is combined with the name of a subprogram, but you can
	specify a prefix that ends with a slash if you wish.
	</p>
	<p>If <code>GCC_EXEC_PREFIX</code> is not set, GCC attempts to figure out
	an appropriate prefix to use based on the pathname it is invoked with.
	</p>
	<p>If GCC cannot find the subprogram using the specified prefix, it
	tries looking in the usual places for the subprogram.
	</p>
	<p>The default value of <code>GCC_EXEC_PREFIX</code> is
	<samp><var>prefix</var>/lib/gcc/</samp> where <var>prefix</var> is the prefix to
	the installed compiler. In many cases <var>prefix</var> is the value
	of <code>prefix</code> when you ran the <samp>configure</samp> script.
	</p>
	<p>Other prefixes specified with <samp>-B</samp> take precedence over this prefix.
	</p>
	<p>This prefix is also used for finding files such as <samp>crt0.o</samp> that are
	used for linking.
	</p>
	<p>In addition, the prefix is used in an unusual way in finding the
	directories to search for header files. For each of the standard
	directories whose name normally begins with ‘<samp>/usr/local/lib/gcc</samp>’
	(more precisely, with the value of <code>GCC_INCLUDE_DIR</code>), GCC tries
	replacing that beginning with the specified prefix to produce an
	alternate directory name. Thus, with <samp>-Bfoo/</samp>, GCC searches
	<samp>foo/bar</samp> just before it searches the standard directory
	<samp>/usr/local/lib/bar</samp>.
	If a standard directory begins with the configured
	<var>prefix</var> then the value of <var>prefix</var> is replaced by
	<code>GCC_EXEC_PREFIX</code> when looking for header files.
	</p>
	</dd>
	<dt><code>COMPILER_PATH</code></dt>
	<dd><a name="index-COMPILER_005fPATH"></a>
	<p>The value of <code>COMPILER_PATH</code> is a colon-separated list of
	directories, much like <code>PATH</code>. GCC tries the directories thus
	specified when searching for subprograms, if it can’t find the
	subprograms using <code>GCC_EXEC_PREFIX</code>.
	</p>
	</dd>
	<dt><code>LIBRARY_PATH</code></dt>
	<dd><a name="index-LIBRARY_005fPATH"></a>
	<p>The value of <code>LIBRARY_PATH</code> is a colon-separated list of
	directories, much like <code>PATH</code>. When configured as a native compiler,
	GCC tries the directories thus specified when searching for special
	linker files, if it can’t find them using <code>GCC_EXEC_PREFIX</code>. Linking
	using GCC also uses these directories when searching for ordinary
	libraries for the <samp>-l</samp> option (but directories specified with
	<samp>-L</samp> come first).
	</p>
	</dd>
	<dt><code>LANG</code></dt>
	<dd><a name="index-LANG-1"></a>
	<a name="index-locale-definition"></a>
	<p>This variable is used to pass locale information to the compiler. One way in
	which this information is used is to determine the character set to be used
	when character literals, string literals and comments are parsed in C and C++.
	When the compiler is configured to allow multibyte characters,
	the following values for <code>LANG</code> are recognized:
	</p>
	<dl compact="compact">
	<dt>‘<samp>C-JIS</samp>’</dt>
	<dd><p>Recognize JIS characters.
	</p></dd>
	<dt>‘<samp>C-SJIS</samp>’</dt>
	<dd><p>Recognize SJIS characters.
	</p></dd>
	<dt>‘<samp>C-EUCJP</samp>’</dt>
	<dd><p>Recognize EUCJP characters.
	</p></dd>
	</dl>

	<p>If <code>LANG</code> is not defined, or if it has some other value, then the
	compiler uses <code>mblen</code> and <code>mbtowc</code> as defined by the default locale to
	recognize and translate multibyte characters.
	</p></dd>
	</dl>

	<p>Some additional environment variables affect the behavior of the
	preprocessor.
	</p>



	<dl compact="compact">
	<dt><code>CPATH</code>
	<a name="index-CPATH"></a>
	</dt>
	<dt><code>C_INCLUDE_PATH</code>
	<a name="index-C_005fINCLUDE_005fPATH"></a>
	</dt>
	<dt><code>CPLUS_INCLUDE_PATH</code>
	<a name="index-CPLUS_005fINCLUDE_005fPATH"></a>
	</dt>
	<dt><code>OBJC_INCLUDE_PATH</code>
	<a name="index-OBJC_005fINCLUDE_005fPATH"></a>
	</dt>
	<dd><p>Each variable’s value is a list of directories separated by a special
	character, much like <code>PATH</code>, in which to look for header files.
	The special character, <code>PATH_SEPARATOR</code>, is target-dependent and
	determined at GCC build time. For Microsoft Windows-based targets it is a
	semicolon, and for almost all other targets it is a colon.
	</p>
	<p><code>CPATH</code> specifies a list of directories to be searched as if
	specified with <samp>-I</samp>, but after any paths given with <samp>-I</samp>
	options on the command line. This environment variable is used
	regardless of which language is being preprocessed.
	</p>
	<p>The remaining environment variables apply only when preprocessing the
	particular language indicated. Each specifies a list of directories
	to be searched as if specified with <samp>-isystem</samp>, but after any
	paths given with <samp>-isystem</samp> options on the command line.
	</p>
	<p>In all these variables, an empty element instructs the compiler to
	search its current working directory. Empty elements can appear at the
	beginning or end of a path. For instance, if the value of
	<code>CPATH</code> is <code>:/special/include</code>, that has the same
	effect as ‘<samp><span class="nolinebreak">-I.</span> <span class="nolinebreak">-I/special/include</span><!-- /@w --></samp>’.
	</p>

	</dd>
	<dt><code>DEPENDENCIES_OUTPUT</code>
	<a name="index-DEPENDENCIES_005fOUTPUT"></a>
	</dt>
	<dd><a name="index-dependencies-for-make-as-output"></a>
	<p>If this variable is set, its value specifies how to output
	dependencies for Make based on the non-system header files processed
	by the compiler. System header files are ignored in the dependency
	output.
	</p>
	<p>The value of <code>DEPENDENCIES_OUTPUT</code> can be just a file name, in
	which case the Make rules are written to that file, guessing the target
	name from the source file name. Or the value can have the form
	‘<samp><var>file</var> <var>target</var></samp>’, in which case the rules are written to
	file <var>file</var> using <var>target</var> as the target name.
	</p>
	<p>In other words, this environment variable is equivalent to combining
	the options <samp>-MM</samp> and <samp>-MF</samp>
	(see <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>),
	with an optional <samp>-MT</samp> switch too.
	</p>
	</dd>
	<dt><code>SUNPRO_DEPENDENCIES</code>
	<a name="index-SUNPRO_005fDEPENDENCIES"></a>
	</dt>
	<dd><a name="index-dependencies-for-make-as-output-1"></a>
	<p>This variable is the same as <code>DEPENDENCIES_OUTPUT</code> (see above),
	except that system header files are not ignored, so it implies
	<samp>-M</samp> rather than <samp>-MM</samp>. However, the dependence on the
	main input file is omitted.
	See <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>.
	</p></dd>
	</dl>


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