EXIT(3) Linux Programmer's Manual EXIT(3)
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 functions 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 termination, respectively.
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 functions with atexit()
and on_exit(). Always the last-registered function is removed from the chain of regis-
tered 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 environ-
ments) than that of 0 and some nonzero value like 1 or -1. In particular, VMS uses a dif-
BSD has attempted to standardize exit codes - see the file <sysexits.h>.
After exit(), the exit status must be transmitted to the parent process. 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 indi-
cated 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 status) 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 controlling terminal
of the session, then each process in the foreground process group of this controlling ter-
minal is sent a SIGHUP signal, and the terminal is disassociated from this session, allow-
ing it to be acquired by a new controlling process.
If the exit of the process causes a process group to become orphaned, and if any member of
the newly-orphaned process group is stopped, then a SIGHUP signal followed by a SIGCONT
signal will be sent to each process in this process group.
_exit(2), wait(2), atexit(3), on_exit(3), tmpfile(3)