exit(3) — Linux manual page


EXIT(3)                   Linux Programmer's Manual                  EXIT(3)

NAME         top

       exit - cause normal process termination

SYNOPSIS         top

       #include <stdlib.h>

       void exit(int status);

DESCRIPTION         top

       The exit() function causes normal process termination and the least
       significant byte of status (i.e., status & 0xFF) is returned to the
       parent (see wait(2)).

       All functions registered with atexit(3) and on_exit(3) are called, in
       the reverse order of their registration.  (It is possible for one of
       these functions to use atexit(3) or on_exit(3) to register an
       additional function to be executed during exit processing; the new
       registration is added to the front of the list of functions that
       remain to be called.)  If one of these functions does not return
       (e.g., it calls _exit(2), or kills itself with a signal), then none
       of the remaining functions is called, and further exit processing (in
       particular, flushing of stdio(3) streams) is abandoned.  If a
       function has been registered multiple times using atexit(3) or
       on_exit(3), then it is called as many times as it was registered.

       All open stdio(3) streams are flushed and closed.  Files created by
       tmpfile(3) are removed.

       The C standard specifies two constants, EXIT_SUCCESS and
       EXIT_FAILURE, that may be passed to exit() to indicate successful or
       unsuccessful termination, respectively.

RETURN VALUE         top

       The exit() function does not return.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface Attribute     Value               │
       │exit()    │ Thread safety │ MT-Unsafe race:exit │
       The exit() function uses a global variable that is not protected, so
       it is not thread-safe.

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

NOTES         top

       The behavior is undefined if one of the functions registered using
       atexit(3) and on_exit(3) calls either exit() or longjmp(3).  Note
       that a call to execve(2) removes registrations created using
       atexit(3) and on_exit(3).

       The use of EXIT_SUCCESS and EXIT_FAILURE is slightly more portable
       (to non-UNIX environments) than the use of 0 and some nonzero value
       like 1 or -1.  In particular, VMS uses a different convention.

       BSD has attempted to standardize exit codes (which some C libraries
       such as the GNU C library have also adopted); see the file

       After exit(), the exit status must be transmitted to the parent
       process.  There are three cases:

       •  If the parent has set SA_NOCLDWAIT, or has set the SIGCHLD handler
          to SIG_IGN, the status is discarded and the child dies

       •  If the parent was waiting on the child, it is notified of the exit
          status and the child dies immediately.

       •  Otherwise, the child becomes a "zombie" process: most of the
          process resources are recycled, but a slot containing minimal
          information about the child process (termination status, resource
          usage statistics) is retained in process table.  This allows the
          parent to subsequently use waitpid(2) (or similar) to learn the
          termination status of the child; at that point the zombie process
          slot is released.

       If the implementation supports the SIGCHLD signal, this signal is
       sent to the parent.  If the parent has set SA_NOCLDWAIT, it is
       undefined whether a SIGCHLD signal is sent.

   Signals sent to other processes
       If the exiting process is a session leader and its controlling
       terminal is the controlling terminal of the session, then each
       process in the foreground process group of this controlling terminal
       is sent a SIGHUP signal, and the terminal is disassociated from this
       session, allowing it to be acquired by a new controlling process.

       If the exit of the process causes a process group to become orphaned,
       and if any member of the newly orphaned process group is stopped,
       then a SIGHUP signal followed by a SIGCONT signal will be sent to
       each process in this process group.  See setpgid(2) for an
       explanation of orphaned process groups.

       Except in the above cases, where the signalled processes may be
       children of the terminating process, termination of a process does
       not in general cause a signal to be sent to children of that process.
       However, a process can use the prctl(2) PR_SET_PDEATHSIG operation to
       arrange that it receives a signal if its parent terminates.

SEE ALSO         top

       _exit(2), get_robust_list(2), setpgid(2), wait(2), atexit(3),
       on_exit(3), tmpfile(3)

COLOPHON         top

       This page is part of release 5.09 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

Linux                            2020-02-09                          EXIT(3)

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