Manpages - _exit.2
Table of Contents
NAME
_exit, _Exit - terminate the calling process
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.
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. The function *_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
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
*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
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