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<a name="tolower_002c-tolower_005fl_002d_002d_002dtranslate-characters-to-lowercase"></a>
<h3 class="section">3.14 <code>tolower</code>, <code>tolower_l</code>&mdash;translate characters to lowercase</h3>
<a name="index-tolower"></a>
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<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">#include &lt;ctype.h&gt;
int tolower(int <var>c</var>);
int _tolower(int <var>c</var>);

#include &lt;ctype.h&gt;
int tolower_l(int <var>c</var>, locale_t <var>locale</var>);

</pre></div>
<p><strong>Description</strong><br>
<code>tolower</code> is a macro which converts uppercase characters to lowercase,
leaving all other characters unchanged.  It is only defined when
<var>c</var> is an integer in the range <code>EOF</code> to <code>255</code>.
</p>
<p><code>tolower_l</code> is like <code>tolower</code> but performs the function based on the
locale specified by the locale object locale.  If <var>locale</var> is
LC_GLOBAL_LOCALE or not a valid locale object, the behaviour is undefined.
</p>
<p>You can use a compiled subroutine instead of the macro definition by
undefining this macro using &lsquo;<code>#undef tolower</code>&rsquo; or &lsquo;<code>#undef tolower_l</code>&rsquo;.
</p>
<p><code>_tolower</code> performs the same conversion as <code>tolower</code>, but should
only be used when <var>c</var> is known to be an uppercase character (<code>A</code>&ndash;<code>Z</code>).
</p>
<br>
<p><strong>Returns</strong><br>
<code>tolower</code>, <code>tolower_l</code> return the lowercase equivalent of <var>c</var> when
<var>c</var> is an uppercase character, and <var>c</var> otherwise.
</p>
<p><code>_tolower</code> returns the lowercase equivalent of <var>c</var> when it is a
character between <code>A</code> and <code>Z</code>.  If <var>c</var> is not one of these
characters, the behaviour of <code>_tolower</code> is undefined.
</p>
<br>
<p><strong>Portability</strong><br>
<code>tolower</code> is ANSI C.  <code>_tolower</code> is not recommended for portable programs.
<code>tolower_l</code> is POSIX-1.2008.
</p>
<p>No supporting OS subroutines are required.
</p>
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