NAME¶
atexit - register a function to be called at normal process termination
SYNOPSIS¶
#include <stdlib.h>
int atexit(void (*function)(void));
DESCRIPTION¶
The
atexit() function registers the given
function to be called at
normal process termination, either via
exit(3) or via return from the
program's
main(). Functions so registered are called in the reverse
order of their registration; no arguments are passed.
The same function may be registered multiple times: it is called once for each
registration.
POSIX.1-2001 requires that an implementation allow at least
ATEXIT_MAX
(32) such functions to be registered. The actual limit supported by an
implementation can be obtained using
sysconf(3).
When a child process is created via
fork(2), it inherits copies of its
parent's registrations. Upon a successful call to one of the
exec(3)
functions, all registrations are removed.
RETURN VALUE¶
The
atexit() function returns the value 0 if successful; otherwise it
returns a nonzero value.
SVr4, 4.3BSD, C89, C99, POSIX.1-2001.
NOTES¶
Functions registered using
atexit() (and
on_exit(3)) are not
called if a process terminates abnormally because of the delivery of a signal.
If one of the functions registered functions calls
_exit(2), then any
remaining functions are not invoked, and the other process termination steps
performed by
exit(3) are not performed.
POSIX.1-2001 says that the result of calling
exit(3) more than once
(i.e., calling
exit(3) within a function registered using
atexit()) is undefined. On some systems (but not Linux), this can
result in an infinite recursion; portable programs should not invoke
exit(3) inside a function registered using
atexit().
The
atexit() and
on_exit(3) functions register functions on the
same list: at normal process termination, the registered functions are invoked
in reverse order of their registration by these two functions.
POSIX.1-2001 says that the result is undefined if
longjmp(3) is used to
terminate execution of one of the functions registered
atexit().
Linux Notes¶
Since glibc 2.2.3,
atexit() (and
on_exit(3)) can be used within a
shared library to establish functions that are called when the shared library
is unloaded.
EXAMPLE¶
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
void
bye(void)
{
printf("That was all, folks\n");
}
int
main(void)
{
long a;
int i;
a = sysconf(_SC_ATEXIT_MAX);
printf("ATEXIT_MAX = %ld\n", a);
i = atexit(bye);
if (i != 0) {
fprintf(stderr, "cannot set exit function\n");
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
SEE ALSO¶
_exit(2),
exit(3),
on_exit(3)
COLOPHON¶
This page is part of release 3.44 of the Linux
man-pages project. A
description of the project, and information about reporting bugs, can be found
at
http://www.kernel.org/doc/man-pages/.