usr.bin/tip/uucplock.c

/*
 * Copyright (c) 1988 The Regents of the University of California.
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 THE REGENTS 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.
 *
 * PATCHES MAGIC                LEVEL   PATCH THAT GOT US HERE
 * --------------------         -----   ----------------------
 * CURRENT PATCH LEVEL:         1       00139
 * --------------------         -----   ----------------------
 *
 * 19 Aug 93    Peter da Silva          Better errors and Taylor UUCP locks
 *
 */

#ifndef lint
static char sccsid[] = "@(#)uucplock.c  5.5 (Berkeley) 6/1/90";
#endif /* not lint */

#include <stdio.h>
#include <sys/types.h>
#include <sys/file.h>
#include <sys/dir.h>
#include <errno.h>
#include "pathnames.h"

/*
 * uucp style locking routines
 * return: 0 - success
 *        -1 - failure
 */

uu_lock(ttyname)
        char *ttyname;
{
        extern int errno;
        int fd, pid;
        char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
        off_t lseek();
        char text_pid[81];      /* PDS 93 */
        int len;                /* PDS 93 */

        (void)sprintf(tbuf, _PATH_LOCKDIRNAME, ttyname);
        fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0660);
        if (fd < 0) {
                /*
                 * file is already locked
                 * check to see if the process holding the lock still exists
                 */
                fd = open(tbuf, O_RDWR, 0);
                if (fd < 0) {
                        perror(tbuf);   /* +PDS 93 */
                        fprintf(stderr, "Can't open lock file.\n");
                        return(-1);
                }
                len = read(fd, text_pid, sizeof(text_pid)-1);
                if(len<=0) {
                        perror(tbuf);
                        (void)close(fd);
                        fprintf(stderr, "Can't read lock file.\n");
                        return(-1);
                }
                text_pid[len] = 0;
                pid = atol(text_pid);   /* -PDS 93 */

                if (kill(pid, 0) == 0 || errno != ESRCH) {
                        (void)close(fd);        /* process is still running */
                        return(-1);
                }
                /*
                 * The process that locked the file isn't running, so
                 * we'll lock it ourselves
                 */
        /* +PDS 93 */
                fprintf(stderr, "Stale lock on %s PID=%d... overriding.\n",
                        ttyname, pid);
                if (lseek(fd, 0L, L_SET) < 0) {
                        perror(tbuf);
                        (void)close(fd);
                        fprintf(stderr, "Can't seek lock file.\n");
                        return(-1);
                }
                /* fall out and finish the locking process */
        }
        pid = getpid();
        sprintf(text_pid, "%10d\n", pid);
        len = strlen(text_pid);
        if (write(fd, text_pid, len) != len) {  /* -PDS 93 */
                (void)close(fd);
                (void)unlink(tbuf);
                perror("lock write");
                return(-1);
        }
        (void)close(fd);
        return(0);
}

uu_unlock(ttyname)
        char *ttyname;
{
        char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];

        (void)sprintf(tbuf, _PATH_LOCKDIRNAME, ttyname);
        return(unlink(tbuf));
}