_exit(2)                                       System Calls Manual                                      _exit(2)

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)

Linux man-pages 6.7                                2023-10-31                                           _exit(2)