atexit(3C) Standard C Library Functions atexit(3C)NAME
atexit - register a function to run at process termination or object unloading
SYNOPSIS
#include <stdlib.h>
int atexit(void (*func)(void));
DESCRIPTION
The atexit() function registers the function pointed to by func to be called without arguments on normal termination of the program or when
the object defining the function is unloaded.
Normal termination occurs by either a call to the exit(3C) function or a return from main(). Object unloading occurs when a call to
dlclose(3C) results in the object becoming unreferenced.
The number of functions that may be registered with atexit() is limited only by available memory (refer to the _SC_ATEXIT_MAX argument of
sysconf(3C)).
After a successful call to any of the exec(2) functions, any functions previously registered by atexit() are no longer registered.
On process exit, functions are called in the reverse order of their registration. On object unloading, any functions belonging to an
unloadable object are called in the reverse order of their registration.
RETURN VALUES
Upon successful completion, the atexit() function returns 0. Otherwise, it returns a non-zero value.
ERRORS
The atexit() function may fail if:
ENOMEM Insufficient storage space is available.
USAGE
The functions registered by a call to atexit() must return to ensure that all registered functions are called.
There is no way for an application to tell how many functions have already been registered with atexit().
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Standard |
+-----------------------------+-----------------------------+
|MT-Level |Safe |
+-----------------------------+-----------------------------+
SEE ALSO exec(2), dlclose(3C), exit(3C), sysconf(3C), attributes(5)SunOS 5.11 25 May 2001 atexit(3C)
Check Out this Related Man Page
ATEXIT(3) Linux Programmer's Manual ATEXIT(3)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 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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
+----------+---------------+---------+
|Interface | Attribute | Value |
+----------+---------------+---------+
|atexit() | Thread safety | MT-Safe |
+----------+---------------+---------+
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
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 termina-
tion steps performed by exit(3) are not performed.
POSIX.1 says that the result of calling exit(3) more than once (i.e., calling exit(3) within a function registered using atexit()) is unde-
fined. 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.
According to POSIX.1, the result is undefined if longjmp(3) is used to terminate execution of one of the functions registered using
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
");
}
int
main(void)
{
long a;
int i;
a = sysconf(_SC_ATEXIT_MAX);
printf("ATEXIT_MAX = %ld
", a);
i = atexit(bye);
if (i != 0) {
fprintf(stderr, "cannot set exit function
");
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
SEE ALSO _exit(2), dlopen(3), exit(3), on_exit(3)COLOPHON
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Linux 2017-09-15 ATEXIT(3)