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atexit

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.

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(), it inherits copies of the its parents registrations. Upon a successful call to one of the exec() functions, all registrations are removed.

RETURN VALUE

The atexit() function returns the value 0 if successful; otherwise it returns a non-zero value.

EXAMPLE

 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 
 void bye(void) {
         printf("That was all, folks\n");
 }
 
 int main(){
         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");
                 return EXIT_FAILURE;
         }
         return EXIT_SUCCESS;
 }
 

NOTES

Since glibc 2.2.3, atexit() (and on_exit()) can be used to within a shared library to establish functions that are called when the shared library is unloaded.

Functions registered using atexit() (and on_exit()) are not called if a process terminates abnormally because of the delivery of a signal.

CONFORMING TO

SVr4, 4.3BSD, C89, C99, POSIX.1-2001.

SEE ALSO

_exit(3), exit(3), on_exit(3)