devdocs/c/program%2Fatexit.html


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    <h1 id="firstHeading" class="firstHeading">atexit</h1>            <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code>&lt;stdlib.h&gt;</code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl"> <td class="t-dcl-nopad"> <pre data-language="c">int atexit( void (*func)(void) );</pre>
</td> <td class="t-dcl-nopad"> </td> <td class="t-dcl-nopad"> </td> </tr>  </table> <p>Registers the function pointed to by <code>func</code> to be called on normal program termination (via <code><a href="exit" title="c/program/exit">exit()</a></code> or returning from <code>main()</code>). The functions will be called in reverse order they were registered, i.e. the function registered last will be executed first.</p>
<p>The same function may be registered more than once.</p>
<p><code>atexit</code> is thread-safe: calling the function from several threads does not induce a data race.</p>
<p>The implementation is guaranteed to support the registration of at least <code>32</code> functions. The exact limit is implementation-defined.</p>
<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> func </td> <td> - </td> <td> pointer to a function to be called on normal program termination </td>
</tr>
</table> <h3 id="Return_value"> Return value</h3> <p><code>0</code> if the registration succeeds, nonzero value otherwise.</p>
<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include &lt;stdlib.h&gt;
#include &lt;stdio.h&gt;
 
void f1(void)
{
    puts("f1");
}
 
void f2(void)
{
    puts("f2");
}
 
int main(void)
{
    if ( ! atexit(f1) &amp;&amp; ! atexit(f2) &amp;&amp; ! atexit(f2) )
        return EXIT_SUCCESS ;
 
    // atexit registration failed
    return EXIT_FAILURE ;
 
}   // &lt;- if registration was successful calls f2, f2, f1</pre></div> <p>Output:</p>
<div class="text source-text"><pre data-language="c">f2
f2
f1</pre></div> </div> <h3 id="References"> References</h3>  <ul>
<li> C17 standard (ISO/IEC 9899:2018): </li>
<ul><li> 7.22.4.2 The atexit function (p: 255) </li></ul>
<li> C11 standard (ISO/IEC 9899:2011): </li>
<ul><li> 7.22.4.2 The atexit function (p: 350) </li></ul>
<li> C99 standard (ISO/IEC 9899:1999): </li>
<ul><li> 7.20.4.2 The atexit function (p: 315) </li></ul>
<li> C89/C90 standard (ISO/IEC 9899:1990): </li>
<ul><li> 7.10.4.2 The atexit function (p: 156) </li></ul>
</ul>               <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="at_quick_exit" title="c/program/at quick exit"> <span class="t-lines"><span>at_quick_exit</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div> </td> <td> registers a function to be called on <a href="quick_exit" title="c/program/quick exit"><code>quick_exit</code></a> invocation <br> <span class="t-mark">(function)</span>  </td>
</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/utility/program/atexit" title="cpp/utility/program/atexit">C++ documentation</a></span> for <code>atexit</code> </td>
</tr> </table>           <div class="_attribution">
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