exit(3) — Linux manual page


exit(3)                 Library Functions Manual                 exit(3)

NAME         top

       exit - cause normal process termination

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <stdlib.h>

       [[noreturn]] 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.

STANDARDS         top

       C11, POSIX.1-2008.

HISTORY         top

       C89, POSIX.1-2001, 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

       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

       •  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)

Linux man-pages (unreleased)   2024-05-02                        exit(3)

Pages that refer to this page: man(1)_exit(2)kill(2)vfork(2)wait(2)abort(3)assert(3)assert_perror(3)atexit(3)err(3)error(3)EXIT_SUCCESS(3const)on_exit(3)pthread_create(3)pthread_detach(3)pthread_exit(3)sd_bus_set_exit_on_disconnect(3)setjmp(3)stdin(3)stdio(3)sysexits.h(3head)tmpfile(3)