1 /*
2 * Copyright (c) 1988 The Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #ifndef lint
35 static char sccsid[] = "@(#)uucplock.c 5.5 (Berkeley) 6/1/90";
36 #endif /* not lint */
37
38 #include <sys/types.h>
39 #include <sys/file.h>
40 #include <sys/dir.h>
41 #include <errno.h>
42 #include "pathnames.h"
43
44 /*
45 * uucp style locking routines
46 * return: 0 - success
47 * -1 - failure
48 */
49
uu_lock(ttyname)50 uu_lock(ttyname)
51 char *ttyname;
52 {
53 extern int errno;
54 int fd, pid;
55 char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
56 off_t lseek();
57
58 (void)sprintf(tbuf, _PATH_LOCKDIRNAME, ttyname);
59 fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0660);
60 if (fd < 0) {
61 /*
62 * file is already locked
63 * check to see if the process holding the lock still exists
64 */
65 fd = open(tbuf, O_RDWR, 0);
66 if (fd < 0) {
67 perror("lock open");
68 return(-1);
69 }
70 if (read(fd, &pid, sizeof(pid)) != sizeof(pid)) {
71 (void)close(fd);
72 perror("lock read");
73 return(-1);
74 }
75
76 if (kill(pid, 0) == 0 || errno != ESRCH) {
77 (void)close(fd); /* process is still running */
78 return(-1);
79 }
80 /*
81 * The process that locked the file isn't running, so
82 * we'll lock it ourselves
83 */
84 if (lseek(fd, 0L, L_SET) < 0) {
85 (void)close(fd);
86 perror("lock lseek");
87 return(-1);
88 }
89 /* fall out and finish the locking process */
90 }
91 pid = getpid();
92 if (write(fd, (char *)&pid, sizeof(pid)) != sizeof(pid)) {
93 (void)close(fd);
94 (void)unlink(tbuf);
95 perror("lock write");
96 return(-1);
97 }
98 (void)close(fd);
99 return(0);
100 }
101
uu_unlock(ttyname)102 uu_unlock(ttyname)
103 char *ttyname;
104 {
105 char tbuf[sizeof(_PATH_LOCKDIRNAME) + MAXNAMLEN];
106
107 (void)sprintf(tbuf, _PATH_LOCKDIRNAME, ttyname);
108 return(unlink(tbuf));
109 }
110