1<html lang="en"> 2<head> 3<title>Environment Variables - The C Preprocessor</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="The C Preprocessor"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="prev" href="Invocation.html#Invocation" title="Invocation"> 9<link rel="next" href="GNU-Free-Documentation-License.html#GNU-Free-Documentation-License" title="GNU Free Documentation License"> 10<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 11<!-- 12Copyright (C) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 131997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 142008, 2009, 2010, 2011 15Free Software Foundation, Inc. 16 17Permission is granted to copy, distribute and/or modify this document 18under the terms of the GNU Free Documentation License, Version 1.3 or 19any later version published by the Free Software Foundation. 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You can use them to specify directories or prefixes to use 66when searching for include files, or to control dependency output. 67 68 <p>Note that you can also specify places to search using options such as 69<samp><span class="option">-I</span></samp>, and control dependency output with options like 70<samp><span class="option">-M</span></samp> (see <a href="Invocation.html#Invocation">Invocation</a>). These take precedence over 71environment variables, which in turn take precedence over the 72configuration of GCC. 73 74<!-- Copyright (c) 1999, 2000, 2001, 2002, 2004 --> 75<!-- Free Software Foundation, Inc. --> 76<!-- This is part of the CPP and GCC manuals. --> 77<!-- For copying conditions, see the file gcc.texi. --> 78<!-- --> 79<!-- Environment variables affecting the preprocessor --> 80<!-- --> 81<!-- If this file is included with the flag ``cppmanual'' set, it is --> 82<!-- formatted for inclusion in the CPP manual; otherwise the main GCC manual. --> 83 <dl> 84<dt><samp><span class="env">CPATH</span></samp><a name="index-CPATH-199"></a><dt><samp><span class="env">C_INCLUDE_PATH</span></samp><a name="index-C_005fINCLUDE_005fPATH-200"></a><dt><samp><span class="env">CPLUS_INCLUDE_PATH</span></samp><a name="index-CPLUS_005fINCLUDE_005fPATH-201"></a><dt><samp><span class="env">OBJC_INCLUDE_PATH</span></samp><a name="index-OBJC_005fINCLUDE_005fPATH-202"></a><dd><!-- Commented out until ObjC++ is part of GCC: --> 85<!-- @itemx OBJCPLUS_INCLUDE_PATH --> 86Each variable's value is a list of directories separated by a special 87character, much like <samp><span class="env">PATH</span></samp>, in which to look for header files. 88The special character, <code>PATH_SEPARATOR</code>, is target-dependent and 89determined at GCC build time. For Microsoft Windows-based targets it is a 90semicolon, and for almost all other targets it is a colon. 91 92 <p><samp><span class="env">CPATH</span></samp> specifies a list of directories to be searched as if 93specified with <samp><span class="option">-I</span></samp>, but after any paths given with <samp><span class="option">-I</span></samp> 94options on the command line. This environment variable is used 95regardless of which language is being preprocessed. 96 97 <p>The remaining environment variables apply only when preprocessing the 98particular language indicated. Each specifies a list of directories 99to be searched as if specified with <samp><span class="option">-isystem</span></samp>, but after any 100paths given with <samp><span class="option">-isystem</span></samp> options on the command line. 101 102 <p>In all these variables, an empty element instructs the compiler to 103search its current working directory. Empty elements can appear at the 104beginning or end of a path. For instance, if the value of 105<samp><span class="env">CPATH</span></samp> is <code>:/special/include</code>, that has the same 106effect as ‘<samp><span class="samp">-I. -I/special/include<!-- /@w --></span></samp>’. 107 108 <!-- man end --> 109 <p>See also <a href="Search-Path.html#Search-Path">Search Path</a>. 110<!-- man begin ENVIRONMENT --> 111 112 <br><dt><samp><span class="env">DEPENDENCIES_OUTPUT</span></samp><a name="index-DEPENDENCIES_005fOUTPUT-203"></a><dd><a name="index-dependencies-for-make-as-output-204"></a>If this variable is set, its value specifies how to output 113dependencies for Make based on the non-system header files processed 114by the compiler. System header files are ignored in the dependency 115output. 116 117 <p>The value of <samp><span class="env">DEPENDENCIES_OUTPUT</span></samp> can be just a file name, in 118which case the Make rules are written to that file, guessing the target 119name from the source file name. Or the value can have the form 120‘<samp><var>file</var> <var>target</var></samp>’, in which case the rules are written to 121file <var>file</var> using <var>target</var> as the target name. 122 123 <p>In other words, this environment variable is equivalent to combining 124the options <samp><span class="option">-MM</span></samp> and <samp><span class="option">-MF</span></samp> 125(see <a href="Invocation.html#Invocation">Invocation</a>), 126with an optional <samp><span class="option">-MT</span></samp> switch too. 127 128 <br><dt><samp><span class="env">SUNPRO_DEPENDENCIES</span></samp><a name="index-SUNPRO_005fDEPENDENCIES-205"></a><dd><a name="index-dependencies-for-make-as-output-206"></a>This variable is the same as <samp><span class="env">DEPENDENCIES_OUTPUT</span></samp> (see above), 129except that system header files are not ignored, so it implies 130<samp><span class="option">-M</span></samp> rather than <samp><span class="option">-MM</span></samp>. However, the dependence on the 131main input file is omitted. 132See <a href="Invocation.html#Invocation">Invocation</a>. 133</dl> 134 <!-- man end --> 135 136<!-- Special handling for inclusion in the install manual. --> 137<!-- man begin DESCRIPTION --> 138 </body></html> 139 140