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89 lines
4.3 KiB
HTML
89 lines
4.3 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>Include Syntax - The C Preprocessor</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="The C Preprocessor">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Header-Files.html#Header-Files" title="Header Files">
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<link rel="next" href="Include-Operation.html#Include-Operation" title="Include Operation">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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Copyright (C) 1987-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation. A copy of
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the license is included in the
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section entitled ``GNU Free Documentation License''.
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This manual contains no Invariant Sections. The Front-Cover Texts are
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(a) (see below), and the Back-Cover Texts are (b) (see below).
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development.
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<style type="text/css"><!--
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--></style>
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</head>
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<body>
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<div class="node">
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<a name="Include-Syntax"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Include-Operation.html#Include-Operation">Include Operation</a>,
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Up: <a rel="up" accesskey="u" href="Header-Files.html#Header-Files">Header Files</a>
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<hr>
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</div>
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<h3 class="section">2.1 Include Syntax</h3>
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<p><a name="index-g_t_0023include-27"></a>Both user and system header files are included using the preprocessing
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directive ‘<samp><span class="samp">#include</span></samp>’. It has two variants:
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<dl>
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<dt><code>#include <</code><var>file</var><code>></code><dd>This variant is used for system header files. It searches for a file
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named <var>file</var> in a standard list of system directories. You can prepend
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directories to this list with the <samp><span class="option">-I</span></samp> option (see <a href="Invocation.html#Invocation">Invocation</a>).
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<br><dt><code>#include "</code><var>file</var><code>"</code><dd>This variant is used for header files of your own program. It
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searches for a file named <var>file</var> first in the directory containing
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the current file, then in the quote directories and then the same
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directories used for <code><</code><var>file</var><code>></code>. You can prepend directories
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to the list of quote directories with the <samp><span class="option">-iquote</span></samp> option.
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</dl>
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<p>The argument of ‘<samp><span class="samp">#include</span></samp>’, whether delimited with quote marks or
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angle brackets, behaves like a string constant in that comments are not
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recognized, and macro names are not expanded. Thus, <code>#include <x/*y><!-- /@w --></code> specifies inclusion of a system header file named <samp><span class="file">x/*y</span></samp>.
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<p>However, if backslashes occur within <var>file</var>, they are considered
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ordinary text characters, not escape characters. None of the character
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escape sequences appropriate to string constants in C are processed.
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Thus, <code>#include "x\n\\y"<!-- /@w --></code> specifies a filename containing three
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backslashes. (Some systems interpret ‘<samp><span class="samp">\</span></samp>’ as a pathname separator.
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All of these also interpret ‘<samp><span class="samp">/</span></samp>’ the same way. It is most portable
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to use only ‘<samp><span class="samp">/</span></samp>’.)
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<p>It is an error if there is anything (other than comments) on the line
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after the file name.
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</body></html>
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