This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

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

       The  application  should call sysconf() 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 atexit().

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

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

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

       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(3POSIX)

       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  atexit()  function shall register the function pointed to by func, to be called without arguments at
       normal program termination. At normal program termination,  all  functions  registered  by  the  atexit()
       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 exit() or a return from main().

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

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

       No errors are defined.

       Thefollowingsectionsareinformative.

       None.

       None.

       atexit — register a function to run at process termination

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

       None.

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

exec, exit(), sysconf()

       The Base Definitions volume of POSIX.1‐2017, <stdlib.h>

       #include <stdlib.h>

       int atexit(void (*func)(void));