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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 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).

       ┌──────────┬───────────────┬─────────────────────┐
       │InterfaceAttributeValue               │
       ├──────────┼───────────────┼─────────────────────┤
       │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

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