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106 lines
4.4 KiB
HTML
106 lines
4.4 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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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<title>freopen (The Red Hat newlib C Library)</title>
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<meta name="description" content="freopen (The Red Hat newlib C Library)">
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<meta name="keywords" content="freopen (The Red Hat newlib C Library)">
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<link href="Document-Index.html#Document-Index" rel="index" title="Document Index">
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<link href="Document-Index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Stdio.html#Stdio" rel="up" title="Stdio">
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</head>
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<body lang="en">
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<a name="freopen"></a>
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<div class="header">
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<p>
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Next: <a href="fseek.html#fseek" accesskey="n" rel="next">fseek</a>, Previous: <a href="fread.html#fread" accesskey="p" rel="prev">fread</a>, Up: <a href="Stdio.html#Stdio" accesskey="u" rel="up">Stdio</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="freopen_002d_002d_002dopen-a-file-using-an-existing-file-descriptor"></a>
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<h3 class="section">4.25 <code>freopen</code>—open a file using an existing file descriptor</h3>
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<a name="index-freopen"></a>
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<a name="index-_005ffreopen_005fr"></a>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">#include <stdio.h>
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FILE *freopen(const char *restrict <var>file</var>, const char *restrict <var>mode</var>,
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FILE *restrict <var>fp</var>);
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FILE *_freopen_r(struct _reent *<var>ptr</var>, const char *restrict <var>file</var>,
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const char *restrict <var>mode</var>, FILE *restrict <var>fp</var>);
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</pre></div>
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<p><strong>Description</strong><br>
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Use this variant of <code>fopen</code> if you wish to specify a particular file
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descriptor <var>fp</var> (notably <code>stdin</code>, <code>stdout</code>, or <code>stderr</code>) for
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the file.
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</p>
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<p>If <var>fp</var> was associated with another file or stream, <code>freopen</code>
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closes that other file or stream (but ignores any errors while closing
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it).
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</p>
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<p><var>file</var> and <var>mode</var> are used just as in <code>fopen</code>.
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</p>
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<p>If <var>file</var> is <code>NULL</code>, the underlying stream is modified rather than
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closed. The file cannot be given a more permissive access mode (for
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example, a <var>mode</var> of "w" will fail on a read-only file descriptor),
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but can change status such as append or binary mode. If modification
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is not possible, failure occurs.
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</p>
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<br>
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<p><strong>Returns</strong><br>
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If successful, the result is the same as the argument <var>fp</var>. If the
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file cannot be opened as specified, the result is <code>NULL</code>.
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</p>
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<br>
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<p><strong>Portability</strong><br>
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ANSI C requires <code>freopen</code>.
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</p>
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<p>Supporting OS subroutines required: <code>close</code>, <code>fstat</code>, <code>isatty</code>,
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<code>lseek</code>, <code>open</code>, <code>read</code>, <code>sbrk</code>, <code>write</code>.
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</p>
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<br>
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</body>
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</html>
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