_EXIT(2) Linux Programmer's Manual _EXIT(2)
_exit, _Exit - terminate the calling process
void _exit(int status);
void _Exit(int status);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_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 oper-
ation). 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.
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. The function _Exit() was in-
troduced 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 fin-
ish. 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 imple-
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
execve(2), exit_group(2), fork(2), kill(2), wait(2), wait4(2), wait-
pid(2), atexit(3), exit(3), on_exit(3), termios(3)
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Linux 2020-02-09 _EXIT(2)