- 论坛徽章:
- 0
|
EXIT(3) Linux Programmer’s Manual EXIT(3)
NAME
exit - cause normal process termination
SYNOPSIS
#include <stdlib.h>
void exit(int status);
DESCRIPTION
The exit() function causes normal process termination and 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. (It is possible for one of these functions to use atexit() or
on_exit() to register an additional function to be executed during exit processing; the new
registration is added to the front of the list of functions that remain to be called.)
All open streams are flushed and closed. Files created by tmpfile() are removed.
The C standard specifies two constants, EXIT_SUCCESS and EXIT_FAILURE, that may be passed
to exit() to indicate successful or unsuccessful termination, respectively.
RETURN VALUE
The exit() function does not return.
CONFORMING TO
SVID 3, POSIX, 4.3BSD, ISO 9899 (‘‘ANSI C’’)
NOTES
It is undefined what happens if one of the functions registered using atexit() and
on_exit() calls either exit() or longjmp().
The use of EXIT_SUCCESS and EXIT_FAILURE is slightly more portable (to non-Unix environ‐
ments) than that of 0 and some non-zero value like 1 or -1. In particular, VMS uses a dif‐
ferent convention.
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 sta‐
tus. 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 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 is 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. |
|