PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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.

NAME         top

       atexit — register a function to run at process termination

SYNOPSIS         top

       #include <stdlib.h>

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

DESCRIPTION         top

       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.1‐2008 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.

RETURN VALUE         top

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

ERRORS         top

       No errors are defined.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       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.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       exec(1p), exit(3p), sysconf(3p)

       The Base Definitions volume of POSIX.1‐2008, stdlib.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/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                 2013                          ATEXIT(3P)