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 <div class="header">
 <p>
 Next: <a href="Search-Path.html#Search-Path" accesskey="n" rel="next">Search Path</a>, Previous: <a href="Include-Syntax.html#Include-Syntax" accesskey="p" rel="prev">Include Syntax</a>, Up: <a href="Header-Files.html#Header-Files" accesskey="u" rel="up">Header Files</a> &nbsp; [<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>
 </div>
 <hr>
 <a name="Include-Operation-1"></a>
 <h3 class="section">2.2 Include Operation</h3>

 <p>The &lsquo;<samp>#include</samp>&rsquo; directive works by directing the C preprocessor to
 scan the specified file as input before continuing with the rest of the
 current file.  The output from the preprocessor contains the output
 already generated, followed by the output resulting from the included
 file, followed by the output that comes from the text after the
 &lsquo;<samp>#include</samp>&rsquo; directive.  For example, if you have a header file
 <samp>header.h</samp> as follows,
 </p>
 <div class="smallexample">
 <pre class="smallexample">char *test (void);
 </pre></div>

 <p>and a main program called <samp>program.c</samp> that uses the header file,
 like this,
 </p>
 <div class="smallexample">
 <pre class="smallexample">int x;
 #include &quot;header.h&quot;

 int
 main (void)
 {
   puts (test ());
 }
 </pre></div>

 <p>the compiler will see the same token stream as it would if
 <samp>program.c</samp> read
 </p>
 <div class="smallexample">
 <pre class="smallexample">int x;
 char *test (void);

 int
 main (void)
 {
   puts (test ());
 }
 </pre></div>

 <p>Included files are not limited to declarations and macro definitions;
 those are merely the typical uses.  Any fragment of a C program can be
 included from another file.  The include file could even contain the
 beginning of a statement that is concluded in the containing file, or
 the end of a statement that was started in the including file.  However,
 an included file must consist of complete tokens.  Comments and string
 literals which have not been closed by the end of an included file are
 invalid.  For error recovery, they are considered to end at the end of
 the file.
 </p>
 <p>To avoid confusion, it is best if header files contain only complete
 syntactic units&mdash;function declarations or definitions, type
 declarations, etc.
 </p>
 <p>The line following the &lsquo;<samp>#include</samp>&rsquo; directive is always treated as a
 separate line by the C preprocessor, even if the included file lacks a
 final newline.
 </p>
 <hr>
 <div class="header">
 <p>
 Next: <a href="Search-Path.html#Search-Path" accesskey="n" rel="next">Search Path</a>, Previous: <a href="Include-Syntax.html#Include-Syntax" accesskey="p" rel="prev">Include Syntax</a>, Up: <a href="Header-Files.html#Header-Files" accesskey="u" rel="up">Header Files</a> &nbsp; [<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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	the license is included in the
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	<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
	<a name="Include-Operation"></a>
	<div class="header">
	<p>
	Next: <a href="Search-Path.html#Search-Path" accesskey="n" rel="next">Search Path</a>, Previous: <a href="Include-Syntax.html#Include-Syntax" accesskey="p" rel="prev">Include Syntax</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>
	</div>
	<hr>
	<a name="Include-Operation-1"></a>
	<h3 class="section">2.2 Include Operation</h3>

	<p>The ‘<samp>#include</samp>’ directive works by directing the C preprocessor to
	scan the specified file as input before continuing with the rest of the
	current file. The output from the preprocessor contains the output
	already generated, followed by the output resulting from the included
	file, followed by the output that comes from the text after the
	‘<samp>#include</samp>’ directive. For example, if you have a header file
	<samp>header.h</samp> as follows,
	</p>
	<div class="smallexample">
	<pre class="smallexample">char *test (void);
	</pre></div>

	<p>and a main program called <samp>program.c</samp> that uses the header file,
	like this,
	</p>
	<div class="smallexample">
	<pre class="smallexample">int x;
	#include "header.h"

	int
	main (void)
	{
	puts (test ());
	}
	</pre></div>

	<p>the compiler will see the same token stream as it would if
	<samp>program.c</samp> read
	</p>
	<div class="smallexample">
	<pre class="smallexample">int x;
	char *test (void);

	int
	main (void)
	{
	puts (test ());
	}
	</pre></div>

	<p>Included files are not limited to declarations and macro definitions;
	those are merely the typical uses. Any fragment of a C program can be
	included from another file. The include file could even contain the
	beginning of a statement that is concluded in the containing file, or
	the end of a statement that was started in the including file. However,
	an included file must consist of complete tokens. Comments and string
	literals which have not been closed by the end of an included file are
	invalid. For error recovery, they are considered to end at the end of
	the file.
	</p>
	<p>To avoid confusion, it is best if header files contain only complete
	syntactic units—function declarations or definitions, type
	declarations, etc.
	</p>
	<p>The line following the ‘<samp>#include</samp>’ directive is always treated as a
	separate line by the C preprocessor, even if the included file lacks a
	final newline.
	</p>
	<hr>
	<div class="header">
	<p>
	Next: <a href="Search-Path.html#Search-Path" accesskey="n" rel="next">Search Path</a>, Previous: <a href="Include-Syntax.html#Include-Syntax" accesskey="p" rel="prev">Include Syntax</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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