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<a name="fputc_002c-fputc_005funlocked_002d_002d_002dwrite-a-character-on-a-stream-or-file"></a>
<h3 class="section">4.20 <code>fputc</code>, <code>fputc_unlocked</code>&mdash;write a character on a stream or file</h3>
<a name="index-fputc"></a>
<a name="index-fputc_005funlocked"></a>
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<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">#include &lt;stdio.h&gt;
int fputc(int <var>ch</var>, FILE *<var>fp</var>);
#define _BSD_SOURCE
#include &lt;stdio.h&gt;
int fputc_unlocked(int <var>ch</var>, FILE *<var>fp</var>);
#include &lt;stdio.h&gt;
int _fputc_r(struct _rent *<var>ptr</var>, int <var>ch</var>, FILE *<var>fp</var>);
#include &lt;stdio.h&gt;
int _fputc_unlocked_r(struct _rent *<var>ptr</var>, int <var>ch</var>, FILE *<var>fp</var>);
</pre></div>
<p><strong>Description</strong><br>
<code>fputc</code> converts the argument <var>ch</var> from an <code>int</code> to an
<code>unsigned char</code>, then writes it to the file or stream identified by
<var>fp</var>.
</p>
<p>If the file was opened with append mode (or if the stream cannot
support positioning), then the new character goes at the end of the
file or stream. Otherwise, the new character is written at the
current value of the position indicator, and the position indicator
oadvances by one.
</p>
<p>For a macro version of this function, see <code>putc</code>.
</p>
<p><code>fputc_unlocked</code> is a non-thread-safe version of <code>fputc</code>.
<code>fputc_unlocked</code> may only safely be used within a scope
protected by flockfile() (or ftrylockfile()) and funlockfile(). This
function may safely be used in a multi-threaded program if and only
if they are called while the invoking thread owns the (FILE *)
object, as is the case after a successful call to the flockfile() or
ftrylockfile() functions. If threads are disabled, then
<code>fputc_unlocked</code> is equivalent to <code>fputc</code>.
</p>
<p>The <code>_fputc_r</code> and <code>_fputc_unlocked_r</code> functions are simply reentrant
versions of the above that take an additional reentrant structure
argument: <var>ptr</var>.
</p>
<br>
<p><strong>Returns</strong><br>
If successful, <code>fputc</code> returns its argument <var>ch</var>. If an error
intervenes, the result is <code>EOF</code>. You can use &lsquo;<code>ferror(<var>fp</var>)</code>&rsquo; to
query for errors.
</p>
<br>
<p><strong>Portability</strong><br>
<code>fputc</code> is required by ANSI C.
</p>
<p><code>fputc_unlocked</code> is a BSD extension also provided by GNU libc.
</p>
<p>Supporting OS subroutines required: <code>close</code>, <code>fstat</code>, <code>isatty</code>,
<code>lseek</code>, <code>read</code>, <code>sbrk</code>, <code>write</code>.
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