NAME

       _exit, _Exit - terminate the calling process

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #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)):

       _Exit():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION

       _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().

RETURN VALUE

       These functions do not return.

STANDARDS

       _exit()
              POSIX.1-2008.

       _Exit()
              C11, POSIX.1-2008.

HISTORY

       POSIX.1-2001, SVr4, 4.3BSD.

       _Exit() was introduced by C99.

NOTES

       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
       The  text  above  in  DESCRIPTION describes the traditional effect of _exit(), which is to
       terminate a process, and these are the semantics specified by POSIX.1 and  implemented  by
       the  C library wrapper function.  On modern systems, this means termination of all threads
       in the process.

       By contrast with the C library  wrapper  function,  the  raw  Linux  _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.

       Up  to  glibc 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.

SEE ALSO

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