ATEXIT(3)                  POSIX Programmer's Manual                 ATEXIT(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NNAAMMEE
       atexit -- register a function to run at process termination

SSYYNNOOPPSSIISS
       #include <stdlib.h>

       int atexit(void (*_f_u_n_c)(void));

DDEESSCCRRIIPPTTIIOONN
       The functionality described on this reference page is aligned with the
       ISO C standard. Any conflict between the requirements described here
       and the ISO C standard is unintentional. This volume of POSIX.1-2017
       defers to the ISO C standard.

       The _a_t_e_x_i_t() function shall register the function pointed to by _f_u_n_c,
       to be called without arguments at normal program termination. At normal
       program termination, all functions registered by the _a_t_e_x_i_t() function
       shall be called, in the reverse order of their registration, except
       that a function is called after any previously registered functions
       that had already been called at the time it was registered.  Normal
       termination occurs either by a call to _e_x_i_t() or a return from _m_a_i_n().

       At least 32 functions can be registered with _a_t_e_x_i_t().

       After a successful call to any of the _e_x_e_c functions, any functions
       previously registered by _a_t_e_x_i_t() shall no longer be registered.

RREETTUURRNN VVAALLUUEE
       Upon successful completion, _a_t_e_x_i_t() shall return 0; otherwise, it
       shall return a non-zero value.

EERRRROORRSS
       No errors are defined.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       None.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       The functions registered by a call to _a_t_e_x_i_t() must return to ensure
       that all registered functions are called.

       The application should call _s_y_s_c_o_n_f() to obtain the value of
       {ATEXIT_MAX}, the number of functions that can be registered. There is
       no way for an application to tell how many functions have already been
       registered with _a_t_e_x_i_t().

       Since the behavior is undefined if the _e_x_i_t() function is called more
       than once, portable applications calling _a_t_e_x_i_t() must ensure that the
       _e_x_i_t() function is not called at normal process termination when all
       functions registered by the _a_t_e_x_i_t() function are called.

       All functions registered by the _a_t_e_x_i_t() function are called at normal
       process termination, which occurs by a call to the _e_x_i_t() function or a
       return from _m_a_i_n() or on the last thread termination, when the behavior
       is as if the implementation called _e_x_i_t() with a zero argument at
       thread termination time.

       If, at normal process termination, a function registered by the
       _a_t_e_x_i_t() function is called and a portable application needs to stop
       further _e_x_i_t() processing, it must call the ___e_x_i_t() function or the
       ___E_x_i_t() function or one of the functions which cause abnormal process
       termination.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _e_x_e_c, _e_x_i_t(), _s_y_s_c_o_n_f()

       The Base Definitions volume of POSIX.1-2017, <<ssttddlliibb..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                            ATEXIT(3)
