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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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ATEXIT(3P) POSIX Programmer's Manual ATEXIT(3P)
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.
atexit — register a function to run at process termination
#include <stdlib.h>
int atexit(void (*func)(void));
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.
Upon successful completion, atexit() shall return 0; otherwise, it
shall return a non-zero value.
No errors are defined.
The following sections are informative.
None.
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.
None.
None.
exec(1p), exit(3p), sysconf(3p)
The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)
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)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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