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| <h3 class="section">2.6 <code>atexit</code>—request execution of functions at program exit</h3> |
| |
| <p><a name="index-atexit-7"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <stdlib.h> |
| int atexit (void (*<var>function</var>)(void)); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| You can use <code>atexit</code> to enroll functions in a list of functions that |
| will be called when your program terminates normally. The argument is |
| a pointer to a user-defined function (which must not require arguments and |
| must not return a result). |
| |
| <p>The functions are kept in a LIFO stack; that is, the last function |
| enrolled by <code>atexit</code> will be the first to execute when your program |
| exits. |
| |
| <p>There is no built-in limit to the number of functions you can enroll |
| in this list; however, after every group of 32 functions is enrolled, |
| <code>atexit</code> will call <code>malloc</code> to get space for the next part of the |
| list. The initial list of 32 functions is statically allocated, so |
| you can always count on at least that many slots available. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>atexit</code> returns <code>0</code> if it succeeds in enrolling your function, |
| <code>-1</code> if it fails (possible only if no space was available for |
| <code>malloc</code> to extend the list of functions). |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| <code>atexit</code> is required by the ANSI standard, which also specifies that |
| implementations must support enrolling at least 32 functions. |
| |
| <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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