/*
 * Copyright (C) 1997 John D. Polstra.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY JOHN D. POLSTRA AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL JOHN D. POLSTRA OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/usr.bin/lockf/lockf.c,v 1.8 1999/08/28 01:03:07 peter Exp $
 */

/*
 * rewritten for use on Solaris by Rojer (myself@rojer.pp.ru)
 * Wed Dec 31 12:59:38 2003
 */

#include <sys/types.h>
#include <sys/wait.h>

#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sysexits.h>
#include <unistd.h>

static int do_open(const char *);
static int do_lock(int, const short);
static void cleanup(void);
static void killed(int sig);
static void timeout(int sig);
static void usage(void);

static const char *lockname;
static int lockfd;
static int keep;
static int locked;
static volatile sig_atomic_t timed_out;

struct flock the_lock;

/*
 * Execute an arbitrary command while holding a file lock.
 */

int
main(int argc, char **argv)
{
    int ch;
    int silent;
    int waitsec;
    int status;
    pid_t child;

    silent = 0;
    keep = 0;
    waitsec = -1;	/* Infinite. */
    lockfd = -1; 	/* not open yet */

    the_lock.l_type = F_WRLCK;
    the_lock.l_whence = SEEK_SET;
    the_lock.l_start = 0;
    the_lock.l_len = 0;

    while ((ch = getopt(argc, argv, "skt:")) != -1) {
	switch (ch) {

	case 'k':
	    keep = 1;
	    break;

	case 's':
	    silent = 1;
	    break;

	case 't':
	    {
		char *endptr;
		waitsec = strtol(optarg, &endptr, 0);
		if (*optarg == '\0' || *endptr != '\0' || waitsec < 0) {
		    fprintf(stderr, "invalid timeout \"%s\"\n", optarg);
		    exit(EX_USAGE);
		    }
	    }
	    break;

	default:
	    usage();
	}
    }
    if (argc - optind < 2)
	usage();
    lockname = argv[optind++];
    argc -= optind;
    argv += optind;

    if (waitsec > 0) {		/* Set up a timeout. */
	struct sigaction act;

	act.sa_handler = timeout;
	sigemptyset(&act.sa_mask);
	act.sa_flags = 0;	/* Note that we do not set SA_RESTART. */

	sigaction(SIGALRM, &act, NULL);
	alarm(waitsec);
    }

    lockfd = do_open(lockname);
    locked = do_lock(lockfd, F_SETLK); /* non-blocking first */
    while (locked == -1 && !timed_out && waitsec != 0) {
	if (lockfd == 1)
		lockfd = do_open(lockname);
	if (locked == -1)
		locked = do_lock(lockfd, F_SETLKW);
	if (lockfd == -1)
		sleep(1);
    	}

    if (waitsec > 0)
	alarm(0);

    if (locked == -1) {		/* We failed to acquire the lock. */
	if (!silent) 
		fprintf(stderr, "%s: already locked\n", lockname);
	exit(EX_TEMPFAIL);
    }

    /* At this point, we own the lock. */

    if (atexit(cleanup) == -1) {
	perror("atexit failed");
	exit(EX_OSERR);
	}

    if ((child = fork()) == -1) {
	perror("cannot fork");
	exit(EX_OSERR);
	}

    if (child == 0) {	/* The child process. */
	close(lockfd);
	execvp(argv[0], argv);
	perror(argv[0]);
	_exit(1);
    }

    /* This is the parent process. */

    signal(SIGINT, SIG_IGN);
    signal(SIGQUIT, SIG_IGN);
    signal(SIGTERM, killed);

    if (waitpid(child, &status, 0) == -1) {
	perror("waitpid failed");
	exit(EX_OSERR);
	}

    return WIFEXITED(status) ? WEXITSTATUS(status) : 1;
}

static int do_open(const char *name) {

	int fd = open(name, O_RDWR|O_CREAT|O_NONBLOCK, 0666);

	if (fd == -1 && errno != EAGAIN && errno != EINTR) {
		perror("open() failed");
                exit(EX_CANTCREAT);
		}

	return fd;
	}

static int do_lock(int fd, const short lock_cmd) {

	int locked;

	if (fd == -1) return -1;
	
	locked = fcntl(fd, lock_cmd, &the_lock);

	if (locked == -1 && errno != EAGAIN && errno != EINTR) {
		perror("fcntl(F_SETLK) failed abnormally");
		exit(EX_OSERR);
		}

	return locked;
	}

/*
 * Remove the lock file.
 */
static void
cleanup(void)
{
    if (keep) {
	the_lock.l_type = F_UNLCK;
	fcntl(lockfd, F_SETLK, &the_lock);
	}
    else
	unlink(lockname);
}

/*
 * Signal handler for SIGTERM.  Cleans up the lock file, then re-raises
 * the signal.
 */
static void
killed(int sig)
{
    cleanup();
    signal(sig, SIG_DFL);
    if (kill(getpid(), sig) == -1) {
	perror("kill failed");
	exit(EX_OSERR);
	}
}

/*
 * Signal handler for SIGALRM.
 */
static void
timeout(int sig)
{
    timed_out = 1;
}

static void
usage(void)
{
    fprintf(stderr,
      "usage: lockf [-ks] [-t seconds] file command [arguments]\n");
    exit(EX_USAGE);
}