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120 lines
5.3 KiB
HTML
120 lines
5.3 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1987-2018 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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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Include Syntax (The C Preprocessor)</title>
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<meta name="description" content="Include Syntax (The C Preprocessor)">
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<meta name="keywords" content="Include Syntax (The C Preprocessor)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Index-of-Directives.html#Index-of-Directives" rel="index" title="Index of Directives">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Header-Files.html#Header-Files" rel="up" title="Header Files">
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<link href="Include-Operation.html#Include-Operation" rel="next" title="Include Operation">
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<link href="Header-Files.html#Header-Files" rel="prev" title="Header Files">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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div.smallexample {margin-left: 3.2em}
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div.smalllisp {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallexample {font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; font-weight: normal}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Include-Syntax"></a>
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<div class="header">
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<p>
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Next: <a href="Include-Operation.html#Include-Operation" accesskey="n" rel="next">Include Operation</a>, Up: <a href="Header-Files.html#Header-Files" accesskey="u" rel="up">Header Files</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index-of-Directives.html#Index-of-Directives" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Include-Syntax-1"></a>
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<h3 class="section">2.1 Include Syntax</h3>
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<a name="index-_0023include"></a>
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<p>Both user and system header files are included using the preprocessing
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directive ‘<samp>#include</samp>’. It has two variants:
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</p>
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<dl compact="compact">
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<dt><code>#include <<var>file</var>></code></dt>
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<dd><p>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>-I</samp> option (see <a href="Invocation.html#Invocation">Invocation</a>).
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</p>
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</dd>
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<dt><code>#include "<var>file</var>"</code></dt>
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<dd><p>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><<var>file</var>></code>. You can prepend directories
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to the list of quote directories with the <samp>-iquote</samp> option.
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</p></dd>
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</dl>
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<p>The argument of ‘<samp>#include</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>x/*y</samp>.
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</p>
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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>\</samp>’ as a pathname separator.
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All of these also interpret ‘<samp>/</samp>’ the same way. It is most portable
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to use only ‘<samp>/</samp>’.)
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</p>
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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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</p>
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</body>
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</html>
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