386BSD 0.1 development

[unix-history] / usr / src / 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.
*/

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

#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();

       (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("lock open");
                       return(-1);
               }
               if (read(fd, &pid, sizeof(pid)) != sizeof(pid)) {
                       (void)close(fd);
                       perror("lock read");
                       return(-1);
               }

               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
                */
               if (lseek(fd, 0L, L_SET) < 0) {
                       (void)close(fd);
                       perror("lock lseek");
                       return(-1);
               }
               /* fall out and finish the locking process */
       }
       pid = getpid();
       if (write(fd, (char *)&pid, sizeof(pid)) != sizeof(pid)) {
               (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));
}