| 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 | |
| 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 | |
| 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 | } |