tinyproxy/src/daemon.c

/* $Id: daemon.c,v 1.6 2005-08-15 18:35:09 rjkaes Exp $
 *
 * This file contains functions which are useful when writing a
 * daemon process.  The functions include a "makedaemon" function and
 * a function to portably set a signal handler.
 *
 * Copyright (C) 2002  Robert James Kaes (rjkaes@users.sourceforge.net)
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */

#include "tinyproxy.h"

#include "daemon.h"

/*
 * Fork a child process and then kill the parent so make the calling
 * program a daemon process.
 */
void
makedaemon(void)
{
        if (fork() != 0)
                exit(0);

        setsid();
        set_signal_handler(SIGHUP, SIG_IGN);

        if (fork() != 0)
                exit(0);

        chdir("/");
        umask(077);

#if NDEBUG
        /*
         * When not in debugging mode, close the standard file
         * descriptors.
         */
        close(0);
        close(1);
        close(2);
#endif
}

/*
 * Pass a signal number and a signal handling function into this function
 * to handle signals sent to the process.
 */
signal_func *
set_signal_handler(int signo, signal_func *func)
{
        struct sigaction act, oact;

        act.sa_handler = func;
        sigemptyset(&act.sa_mask);
        act.sa_flags = 0;
        if (signo == SIGALRM) {
#ifdef SA_INTERRUPT
                act.sa_flags |= SA_INTERRUPT;   /* SunOS 4.x */
#endif
        } else {
#ifdef SA_RESTART
                act.sa_flags |= SA_RESTART;     /* SVR4, 4.4BSD */
#endif
        }

        if (sigaction(signo, &act, &oact) < 0)
                return SIG_ERR;

        return oact.sa_handler;
}