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) 1987-2013 Free Software Foundation, Inc. 13 14Permission is granted to copy, distribute and/or modify this document 15under the terms of the GNU Free Documentation License, Version 1.3 or 16any later version published by the Free Software Foundation. A copy of 17the license is included in the 18section entitled ``GNU Free Documentation License''. 19 20This manual contains no Invariant Sections. The Front-Cover Texts are 21(a) (see below), and the Back-Cover Texts are (b) (see below). 22 23(a) The FSF's Front-Cover Text is: 24 25 A GNU Manual 26 27(b) The FSF's Back-Cover Text is: 28 29 You have freedom to copy and modify this GNU Manual, like GNU 30 software. Copies published by the Free Software Foundation raise 31 funds for GNU development. 32--> 33<meta http-equiv="Content-Style-Type" content="text/css"> 34<style type="text/css"><!-- 35 pre.display { font-family:inherit } 36 pre.format { font-family:inherit } 37 pre.smalldisplay { font-family:inherit; font-size:smaller } 38 pre.smallformat { font-family:inherit; font-size:smaller } 39 pre.smallexample { font-size:smaller } 40 pre.smalllisp { font-size:smaller } 41 span.sc { font-variant:small-caps } 42 span.roman { font-family:serif; font-weight:normal; } 43 span.sansserif { font-family:sans-serif; font-weight:normal; } 44--></style> 45<link rel="stylesheet" type="text/css" href="../cs.css"> 46</head> 47<body> 48<div class="node"> 49<a name="Environment-Variables"></a> 50<p> 51Next: <a rel="next" accesskey="n" href="GNU-Free-Documentation-License.html#GNU-Free-Documentation-License">GNU Free Documentation License</a>, 52Previous: <a rel="previous" accesskey="p" href="Invocation.html#Invocation">Invocation</a>, 53Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a> 54<hr> 55</div> 56 57<h2 class="chapter">13 Environment Variables</h2> 58 59<p><a name="index-environment-variables-203"></a><!-- man begin ENVIRONMENT --> 60 61 <p>This section describes the environment variables that affect how CPP 62operates. You can use them to specify directories or prefixes to use 63when searching for include files, or to control dependency output. 64 65 <p>Note that you can also specify places to search using options such as 66<samp><span class="option">-I</span></samp>, and control dependency output with options like 67<samp><span class="option">-M</span></samp> (see <a href="Invocation.html#Invocation">Invocation</a>). These take precedence over 68environment variables, which in turn take precedence over the 69configuration of GCC. 70 71<!-- Copyright (C) 1999-2013 Free Software Foundation, Inc. --> 72<!-- This is part of the CPP and GCC manuals. --> 73<!-- For copying conditions, see the file gcc.texi. --> 74<!-- --> 75<!-- Environment variables affecting the preprocessor --> 76<!-- --> 77<!-- If this file is included with the flag ``cppmanual'' set, it is --> 78<!-- formatted for inclusion in the CPP manual; otherwise the main GCC manual. --> 79 <dl> 80<dt><samp><span class="env">CPATH</span></samp><a name="index-CPATH-204"></a><dt><samp><span class="env">C_INCLUDE_PATH</span></samp><a name="index-C_005fINCLUDE_005fPATH-205"></a><dt><samp><span class="env">CPLUS_INCLUDE_PATH</span></samp><a name="index-CPLUS_005fINCLUDE_005fPATH-206"></a><dt><samp><span class="env">OBJC_INCLUDE_PATH</span></samp><a name="index-OBJC_005fINCLUDE_005fPATH-207"></a><dd><!-- Commented out until ObjC++ is part of GCC: --> 81<!-- @itemx OBJCPLUS_INCLUDE_PATH --> 82Each variable's value is a list of directories separated by a special 83character, much like <samp><span class="env">PATH</span></samp>, in which to look for header files. 84The special character, <code>PATH_SEPARATOR</code>, is target-dependent and 85determined at GCC build time. For Microsoft Windows-based targets it is a 86semicolon, and for almost all other targets it is a colon. 87 88 <p><samp><span class="env">CPATH</span></samp> specifies a list of directories to be searched as if 89specified with <samp><span class="option">-I</span></samp>, but after any paths given with <samp><span class="option">-I</span></samp> 90options on the command line. This environment variable is used 91regardless of which language is being preprocessed. 92 93 <p>The remaining environment variables apply only when preprocessing the 94particular language indicated. Each specifies a list of directories 95to be searched as if specified with <samp><span class="option">-isystem</span></samp>, but after any 96paths given with <samp><span class="option">-isystem</span></samp> options on the command line. 97 98 <p>In all these variables, an empty element instructs the compiler to 99search its current working directory. Empty elements can appear at the 100beginning or end of a path. For instance, if the value of 101<samp><span class="env">CPATH</span></samp> is <code>:/special/include</code>, that has the same 102effect as ‘<samp><span class="samp">-I. -I/special/include<!-- /@w --></span></samp>’. 103 104 <!-- man end --> 105 <p>See also <a href="Search-Path.html#Search-Path">Search Path</a>. 106<!-- man begin ENVIRONMENT --> 107 108 <br><dt><samp><span class="env">DEPENDENCIES_OUTPUT</span></samp><a name="index-DEPENDENCIES_005fOUTPUT-208"></a><dd><a name="index-dependencies-for-make-as-output-209"></a>If this variable is set, its value specifies how to output 109dependencies for Make based on the non-system header files processed 110by the compiler. System header files are ignored in the dependency 111output. 112 113 <p>The value of <samp><span class="env">DEPENDENCIES_OUTPUT</span></samp> can be just a file name, in 114which case the Make rules are written to that file, guessing the target 115name from the source file name. Or the value can have the form 116‘<samp><var>file</var> <var>target</var></samp>’, in which case the rules are written to 117file <var>file</var> using <var>target</var> as the target name. 118 119 <p>In other words, this environment variable is equivalent to combining 120the options <samp><span class="option">-MM</span></samp> and <samp><span class="option">-MF</span></samp> 121(see <a href="Invocation.html#Invocation">Invocation</a>), 122with an optional <samp><span class="option">-MT</span></samp> switch too. 123 124 <br><dt><samp><span class="env">SUNPRO_DEPENDENCIES</span></samp><a name="index-SUNPRO_005fDEPENDENCIES-210"></a><dd><a name="index-dependencies-for-make-as-output-211"></a>This variable is the same as <samp><span class="env">DEPENDENCIES_OUTPUT</span></samp> (see above), 125except that system header files are not ignored, so it implies 126<samp><span class="option">-M</span></samp> rather than <samp><span class="option">-MM</span></samp>. However, the dependence on the 127main input file is omitted. 128See <a href="Invocation.html#Invocation">Invocation</a>. 129</dl> 130 <!-- man end --> 131 132<!-- Special handling for inclusion in the install manual. --> 133<!-- man begin DESCRIPTION --> 134 </body></html> 135 136