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/* -*- mode: c; c-file-style: "BSD"; -*-
*
* Update Daemon for Linux (and possibly other Unixen).
* Copyright (c) 1996, 1997 Torsten Poulin.
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $RCSfile: update.c,v $
* $Author: torsten $
* $Date: 1997/02/13 17:32:41 $
* $Revision: 1.3 $
*/
#include <stdio.h>
#include <unistd.h>
#include <limits.h>
#include <stdlib.h>
#include <signal.h>
/*
* If NO_BDFLUSH is defined, make this a traditional update
* daemon that calls sync(). This is the default for systems
* other than Linux.
*/
#ifdef __linux__
# include <asm/unistd.h>
# if defined(__GLIBC__) && __GLIBC__ >= 2
# include <sys/kdaemon.h>
# else
_syscall2(int, bdflush, int, func, int, data);
# endif
#else
# ifndef NO_BDFLUSH
# define NO_BDFLUSH
# endif
#endif
#ifdef NO_BDFLUSH
# define ARGS "s:"
#else
# define ARGS "Ss:f:"
# include <syslog.h>
#endif
/*
* OPEN_MAX is POSIX.1
*/
#ifndef OPEN_MAX
# define OPEN_MAX 256 /* anybody's guess */
#endif
static const char RCS[] = "@(#) $Revision: 1.3 $";
unsigned int sync_duration = 30;
unsigned int flush_duration = 5;
int use_sync = 0;
void usage(char *name)
{
fprintf(stderr,
#ifdef NO_BDFLUSH
"Usage: %s [-s secs]\n",
#else
"Usage: %s [-S] [-s secs] [-f secs]\n",
#endif
name);
exit (1);
}
/*
* The update() function never returns.
* If bdflush() fails, it reverts to sync() instead.
*/
void
update(void)
{
for (;;) {
#ifndef NO_BDFLUSH
if (use_sync) {
#endif
sleep(sync_duration);
sync();
#ifndef NO_BDFLUSH
} else {
sleep(flush_duration);
if (bdflush(1, 0) < 0) {
use_sync = 1;
openlog("update", LOG_CONS, LOG_DAEMON);
syslog(LOG_INFO, "Switching to sync(2) instead of bdflush(2)");
closelog();
}
}
#endif
}
}
int
main(int argc, char **argv)
{
int f, c;
while ((c = getopt(argc, argv, ARGS)) != -1)
switch (c) {
case 'S': use_sync = 1; break;
case 's': sync_duration = atoi(optarg); break;
case 'f': flush_duration = atoi(optarg); break;
case '?': usage(argv[0]);
default: abort();
}
if (sync_duration == 0 || flush_duration == 0) {
fprintf(stderr, "%s: argument must be positive integer.\n", argv[0]);
exit(1);
}
if (optind < argc)
usage(argv[0]);
/*
* Prevent people from launching more update daemons.
* Might as well call sync().
*/
if (geteuid() != 0) {
sync();
fprintf(stderr, "%s: should only be run by root.\n", argv[0]);
exit(1);
}
/*
* Ignore a few signals for good measure.
*/
signal(SIGTERM, SIG_IGN);
signal(SIGINT, SIG_IGN);
if (fork() > 0)
exit(0);
/*
* Become session leader (get rid of controlling terminal).
*/
setsid();
/*
* Make sure we are on a file system that stays mounted.
*/
chdir("/");
for (f = 0; f < OPEN_MAX; f++)
close(f);
update();
return 0;
}
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