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130 lines
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<a name="fread"></a>
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<div class="header">
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<p>
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Next: <a href="freopen.html#freopen" accesskey="n" rel="next">freopen</a>, Previous: <a href="fputws.html#fputws" accesskey="p" rel="prev">fputws</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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<hr>
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<a name="fread_002c-fread_005funlocked_002d_002d_002dread-array-elements-from-a-file"></a>
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<h3 class="section">4.24 <code>fread</code>, <code>fread_unlocked</code>—read array elements from a file</h3>
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<a name="index-fread"></a>
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<a name="index-fread_005funlocked"></a>
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<a name="index-_005ffread_005fr"></a>
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<a name="index-_005ffread_005funlocked_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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size_t fread(void *restrict <var>buf</var>, size_t <var>size</var>, size_t <var>count</var>,
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FILE *restrict <var>fp</var>);
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#define _BSD_SOURCE
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#include <stdio.h>
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size_t fread_unlocked(void *restrict <var>buf</var>, size_t <var>size</var>, size_t <var>count</var>,
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FILE *restrict <var>fp</var>);
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#include <stdio.h>
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size_t _fread_r(struct _reent *<var>ptr</var>, void *restrict <var>buf</var>,
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size_t <var>size</var>, size_t <var>count</var>, FILE *restrict <var>fp</var>);
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#include <stdio.h>
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size_t _fread_unlocked_r(struct _reent *<var>ptr</var>, void *restrict <var>buf</var>,
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size_t <var>size</var>, size_t <var>count</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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<code>fread</code> attempts to copy, from the file or stream identified by
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<var>fp</var>, <var>count</var> elements (each of size <var>size</var>) into memory,
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starting at <var>buf</var>. <code>fread</code> may copy fewer elements than
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<var>count</var> if an error, or end of file, intervenes.
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</p>
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<p><code>fread</code> also advances the file position indicator (if any) for
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<var>fp</var> by the number of <em>characters</em> actually read.
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</p>
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<p><code>fread_unlocked</code> is a non-thread-safe version of <code>fread</code>.
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<code>fread_unlocked</code> may only safely be used within a scope
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protected by flockfile() (or ftrylockfile()) and funlockfile(). This
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function may safely be used in a multi-threaded program if and only
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if they are called while the invoking thread owns the (FILE *)
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object, as is the case after a successful call to the flockfile() or
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ftrylockfile() functions. If threads are disabled, then
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<code>fread_unlocked</code> is equivalent to <code>fread</code>.
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</p>
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<p><code>_fread_r</code> and <code>_fread_unlocked_r</code> are simply reentrant versions of the
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above that take an additional reentrant structure pointer argument: <var>ptr</var>.
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</p>
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<br>
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<p><strong>Returns</strong><br>
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The result of <code>fread</code> is the number of elements it succeeded in
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reading.
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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>fread</code>.
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</p>
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<p><code>fread_unlocked</code> is a BSD extension also provided by GNU libc.
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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>read</code>, <code>sbrk</code>, <code>write</code>.
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</p>
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<br>
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<hr>
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<div class="header">
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<p>
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Next: <a href="freopen.html#freopen" accesskey="n" rel="next">freopen</a>, Previous: <a href="fputws.html#fputws" accesskey="p" rel="prev">fputws</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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