_exit - terminate the current process
_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.
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.
_exit never returns.
SVr4, SVID, POSIX, X/OPEN, BSD 4.3
_exit does not call any functions registered with the ANSI C atexit function and does not flush standard I/O buffers. To do these things, use exit(3).