exit

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



NAME
       exit - cause normal process termination

SYNOPSIS
       #include <stdlib.h>

       noreturn void exit(int status);

DESCRIPTION
       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
       The exit() function does not return.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────────────────────────┬───────────────┬─────────────────────┐
       │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
       POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

NOTES
       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 <sysexits.h>.

       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 immediately.

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

COLOPHON
       This page is part of release 5.13 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
       https://www.kernel.org/doc/man-pages/.



Linux                              2021-03-22                            EXIT(3)