1 /* 2 * Copyright (c) 1988, 1993 3 * The Regents of the University of California. 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 * $Id$ 34 * 35 */ 36 37 #ifndef lint 38 static const char sccsid[] = "@(#)uucplock.c 8.1 (Berkeley) 6/6/93"; 39 #endif /* not lint */ 40 41 #include <sys/types.h> 42 #include <sys/file.h> 43 #include <dirent.h> 44 #include <errno.h> 45 #include <unistd.h> 46 #include <signal.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <paths.h> 50 #include <string.h> 51 #include "libutil.h" 52 53 #define LOCKFMT "LCK..%s" 54 55 /* Forward declarations */ 56 static int put_pid (int fd, pid_t pid); 57 static pid_t get_pid (int fd,int *err); 58 59 /* 60 * uucp style locking routines 61 * return: 0 - success 62 * -1 - failure 63 */ 64 65 int uu_lock (char *ttyname) 66 { 67 int fd; 68 pid_t pid; 69 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 70 int err; 71 72 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname); 73 fd = open(tbuf, O_RDWR|O_CREAT|O_EXCL, 0660); 74 if (fd < 0) { 75 /* 76 * file is already locked 77 * check to see if the process holding the lock still exists 78 */ 79 fd = open(tbuf, O_RDWR, 0); 80 if (fd < 0) 81 return UU_LOCK_OPEN_ERR; 82 83 if ((pid = get_pid (fd, &err)) == -1) { 84 (void)close(fd); 85 errno = err; 86 return UU_LOCK_READ_ERR; 87 } 88 89 if (kill(pid, 0) == 0 || errno != ESRCH) { 90 (void)close(fd); /* process is still running */ 91 return UU_LOCK_INUSE; 92 } 93 /* 94 * The process that locked the file isn't running, so 95 * we'll lock it ourselves 96 */ 97 if (lseek(fd, (off_t) 0, L_SET) < 0) { 98 err = errno; 99 (void)close(fd); 100 errno = err; 101 return UU_LOCK_SEEK_ERR; 102 } 103 /* fall out and finish the locking process */ 104 } 105 pid = getpid(); 106 if (!put_pid (fd, pid)) { 107 err = errno; 108 (void)close(fd); 109 (void)unlink(tbuf); 110 errno = err; 111 return UU_LOCK_WRITE_ERR; 112 } 113 (void)close(fd); 114 return UU_LOCK_OK; 115 } 116 117 int uu_unlock (char *ttyname) 118 { 119 char tbuf[sizeof(_PATH_UUCPLOCK) + MAXNAMLEN]; 120 121 (void)snprintf(tbuf, sizeof(tbuf), _PATH_UUCPLOCK LOCKFMT, ttyname); 122 return unlink(tbuf); 123 } 124 125 char *uu_lockerr (int uu_lockresult) 126 { 127 static char errbuf[128]; 128 char *fmt; 129 130 switch (uu_lockresult) { 131 case UU_LOCK_INUSE: 132 return "device in use"; 133 case UU_LOCK_OK: 134 return ""; 135 case UU_LOCK_OPEN_ERR: 136 fmt = "open error: %s"; 137 break; 138 case UU_LOCK_READ_ERR: 139 fmt = "read error: %s"; 140 break; 141 case UU_LOCK_SEEK_ERR: 142 fmt = "seek error: %s"; 143 break; 144 case UU_LOCK_WRITE_ERR: 145 fmt = "write error: %s"; 146 break; 147 default: 148 fmt = "undefined error: %s"; 149 break; 150 } 151 152 (void)snprintf(errbuf, sizeof(errbuf), fmt, strerror(errno)); 153 return errbuf; 154 } 155 156 static int put_pid (int fd, pid_t pid) 157 { 158 char buf[32]; 159 int len; 160 161 len = sprintf (buf, "%10d\n", pid); 162 return write (fd, buf, len) == len; 163 } 164 165 static pid_t get_pid (int fd,int *err) 166 { 167 int bytes_read; 168 char buf[32]; 169 pid_t pid; 170 171 bytes_read = read (fd, buf, sizeof (buf) - 1); 172 if (bytes_read > 0) { 173 buf[bytes_read] = '\0'; 174 pid = strtol (buf, (char **) NULL, 10); 175 } else { 176 pid = -1; 177 *err = bytes_read ? errno : EINVAL; 178 } 179 return pid; 180 } 181 182 /* end of uucplock.c */ 183