[...]
       exit [n]
              Cause the shell to exit with a status of n.  If n is omitted, the  exit  status  is
              that  of  the  last  command executed.  A trap on EXIT is executed before the shell
              terminates.
[...]





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

NAME
       exit - cause normal process termination

SYNOPSIS
       #include <stdlib.h>

       void exit(int status);

DESCRIPTION
       The exit() function causes normal process termination and the value of status & 0377 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 reg‐
       ister 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 func‐
       tions 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 con‐
       vention.

       BSD has attempted to standardize exit codes; 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, re‐
          source usage statistics) is retained in process table.  This  allows  the  parent  to  subse‐
          quently  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 ter‐
       minal of the session, then each process in the foreground process group of this controlling ter‐
       minal  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 4.16 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                                          2017-09-15                                       EXIT(3)

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