atexit(3p) — Linux manual page

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

PROLOG

       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

       atexit — register a function to run at process termination

SYNOPSIS

       #include <stdlib.h>

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

DESCRIPTION

       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.

RETURN VALUE

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

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       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

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

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

       The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)

COPYRIGHT

       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(3P)

Pages that refer to this page: stdlib.h(0p), exec(3p), exit(3p), _Exit(3p), fclose(3p), pthread_atfork(3p)

---