exit - cause normal program termination
void exit(int status);
The exit() function causes normal program termination and the the value
of status & 0377 is returned to the parent (see wait(2)). All func-
tions registered with atexit() and on_exit() are called in the reverse
order of their registration, and all open streams are flushed and
closed. Files created by tmpfile() are removed.
The C standard specifies two defines EXIT_SUCCESS and EXIT_FAILURE that
may be passed to exit() to indicate successful or unsuccessful termina-
The exit() function does not return.
SVID 3, POSIX, BSD 4.3, ISO 9899 (``ANSI C'')
During the exit processing, it is possible to register additional func-
tions with atexit() and on_exit(). Always the last-registered function
is removed from the chain of registered functions, and invoked. It is
undefined what happens if during this processing either exit() or
longjmp() is called.
The use of EXIT_SUCCESS and EXIT_FAILURE is slightly more portable (to
non-Unix environments) than that of 0 and some nonzero value like 1 or
-1. In particular, VMS uses a different convention.
BSD has attempted to standardize exit codes - see the file <sysex-
After exit(), the exit status must be transmitted to the parent pro-
cess. There are three cases. If the parent has set SA_NOCLDWAIT, or has
set the SIGCHLD handler to SIG_IGN, the status is discarded. If the
parent was waiting on the child it is notified of the exit status. In
both cases the exiting process dies immediately. If the parent has not
indicated that it is not interested in the exit status, but is not
waiting, the exiting process turns into a "zombie" process (which is
nothing but a container for the single byte representing the exit sta-
tus) so that the parent can learn the exit status when it later calls
one of the wait() functions.
If the implementation supports the SIGCHLD signal, this signal is sent
to the parent. If the parent has set SA_NOCLDWAIT, it is undefined
whether a SIGCHLD signal is sent.
If the process is a session leader and its controlling terminal the
_exit(2), wait(2), atexit(3), on_exit(3), tmpfile(3)