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       exit - cause normal process termination


       #include <stdlib.h>

       void exit(int status);


       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.


       The exit() function does not return.


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


       It  is  undefined what happens if one of the functions registered using
       atexit(3) and on_exit(3) calls either exit() or longjmp(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; 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.  If
       the parent was waiting on the child it is notified of the exit  status.
       In  both cases the exiting process dies immediately.  If the parent has
       not indicated that it is not interested in the exit status, but is  not
       waiting,  the  exiting  process turns into a "zombie" process (which is
       nothing but a container for  the  single  byte  representing  the  exit
       status)  so  that  the  parent  can learn the exit status when it later
       calls one of the wait(2) functions.

       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.

       If the 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.


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


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