Ubuntu manuals

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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 nor‐
        mal process termination, either via exit(3) or via return from the pro‐
        gram’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(2), it inherits copies of its
        parent’s registrations.  Upon a successful call to one of  the  exec(3)
        functions, all registrations are removed.
        The  atexit()  function returns the value 0 if successful; otherwise it
        returns a non-zero 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.
 
    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");
               return EXIT_FAILURE;
            }
            return EXIT_SUCCESS;
        }
        _exit(2), exit(3), on_exit(3)