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       _exit, _Exit - terminate the calling process


       #include <unistd.h>

       noreturn void _exit(int status);

       #include <stdlib.h>

       noreturn void _Exit(int status);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L


       _exit() terminates the calling process "immediately".  Any open file descriptors belonging
       to the process are closed.  Any children of the process are inherited by  init(1)  (or  by
       the   nearest   "subreaper"   process   as   defined  through  the  use  of  the  prctl(2)
       PR_SET_CHILD_SUBREAPER operation).  The process's parent is sent a SIGCHLD signal.

       The value status & 0xFF is returned to the parent process as the  process's  exit  status,
       and can be collected by the parent using one of the wait(2) family of calls.

       The function _Exit() is equivalent to _exit().


       These functions do not return.


       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.  The function _Exit() was introduced by C99.


       For  a  discussion  on  the  effects  of  an exit, the transmission of exit status, zombie
       processes, signals sent, and so on, see exit(3).

       The function _exit() is like exit(3), but does not  call  any  functions  registered  with
       atexit(3)  or  on_exit(3).   Open  stdio(3)  streams  are not flushed.  On the other hand,
       _exit() does close open file descriptors, and this may cause an unknown delay, waiting for
       pending  output  to finish.  If the delay is undesired, it may be useful to call functions
       like tcflush(3) before calling _exit().  Whether any pending I/O is  canceled,  and  which
       pending I/O may be canceled upon _exit(), is implementation-dependent.

   C library/kernel differences
       In glibc up to version 2.3, the _exit() wrapper function invoked the kernel system call of
       the same name.  Since glibc 2.3, the wrapper function invokes exit_group(2), in  order  to
       terminate all of the threads in a process.

       The  raw  _exit()  system  call  terminates  only  the calling thread, and actions such as
       reparenting child processes or sending SIGCHLD to the parent process are performed only if
       this is the last thread in the thread group.


       execve(2),  exit_group(2),  fork(2),  kill(2),  wait(2),  wait4(2), waitpid(2), atexit(3),
       exit(3), on_exit(3), termios(3)


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