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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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_exit(2) System Calls Manual _exit(2)
_exit, _Exit - terminate the calling process
Standard C library (libc, -lc)
#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
_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.
_exit()
POSIX.1-2008.
_Exit()
C11, POSIX.1-2008.
POSIX.1-2001, SVr4, 4.3BSD.
_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
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.
execve(2), exit_group(2), fork(2), kill(2), wait(2), wait4(2),
waitpid(2), atexit(3), exit(3), on_exit(3), termios(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 _exit(2)
Pages that refer to this page: clone(2), exit_group(2), fork(2), kill(2), ptrace(2), seccomp(2), setsid(2), shmop(2), syscalls(2), vfork(2), wait(2), atexit(3), daemon(3), exit(3), on_exit(3), pmgetconfig(3), pmnomem(3), system(3), persistent-keyring(7), signal-safety(7), socket(7), user-keyring(7), user-session-keyring(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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