The
_Exit() and
_exit() functions are equivalent. They each terminate a process with the following consequences:
•
All of the descriptors open in the calling process are closed. This may entail delays, for example, waiting for output to drain; a process in this state may not be killed, as it is already dying.
•
If the parent process of the calling process has an outstanding
wait(2) call or catches the
SIGCHLD signal, it is notified of the calling process's termination and the
status is set as defined by
wait(2).
•
The parent process-ID of all of the calling process's existing child processes are set to 1; the initialization process (see the DEFINITIONS section of
intro(2)) inherits each of these processes.
•
If the termination of the process causes any process group to become orphaned (usually because the parents of all members of the group have now exited; see “orphaned process group” in
intro(2)), and if any member of the orphaned group is stopped, the
SIGHUP signal and the
SIGCONT signal are sent to all members of the newly-orphaned process group.
•
If the process is a controlling process (see
intro(2)), the
SIGHUP signal is sent to the foreground process group of the controlling terminal, and all current access to the controlling terminal is revoked.
Most C programs call the library routine
exit(3), which flushes buffers, closes streams, unlinks temporary files, etc., before calling
_exit().