_exit(2) — Linux manual page


_EXIT(2)                Linux Programmer's Manual               _EXIT(2)

NAME         top

       _exit, _Exit - terminate the calling process

SYNOPSIS         top

       #include <unistd.h>

       noreturn void _exit(int status);

       #include <stdlib.h>

       noreturn void _Exit(int status);

   Feature Test Macro Requirements for glibc (see

           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION         top

       _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         top

       These functions do not return.

CONFORMING TO         top

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

NOTES         top

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

       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.

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

Linux                          2021-03-22                       _EXIT(2)

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