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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 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. 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. CONFORMING TO 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 in- finite 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 in- voked 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 3.74 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/. Linux 2008-12-05 ATEXIT(3)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON
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