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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.


       For   an   explanation   of   the  terms  used  in  this  section,  see

       │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.


       POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.


       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

       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 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

       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.


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


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