_exit(2) -- Linux man page
NAME_exit, _Exit - terminate the current process
void _exit(int status);
DESCRIPTIONThe function _exit terminates the calling process "immediately". Any open file descriptors belonging to the process are closed; any children of the process are inherited by process 1, init, and the process's parent is sent a SIGCHLD signal.
The value status is returned to the parent process as the process's exit status, and can be collected using one of the wait family of calls.
RETURN VALUEThese functions do not return.
CONFORMING TOSVr4, SVID, POSIX, X/OPEN, BSD 4.3. The function _Exit() was introduced by C99.
NOTESFor a discussion on the effects of an exit, the transmission of exit status, zombie processes, signals sent, etc., see exit(3).
The function _exit is like exit(), but does not call any functions registered with the ANSI C atexit function, nor any registered signal handlers. Whether it flushes standard I/O buffers and removes temporary files created with tmpfile(3) is implementation-dependent. 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() before calling _exit(). Whether any pending I/O is cancelled, and which pending I/O may be cancelled upon _exit(), is implementation-dependent.
SEE ALSOfork(2), execve(2), waitpid(2), wait4(2), kill(2), wait(2), exit(3), termios(3)