1 /* 2 * Copyright (C) 1997 John D. Polstra. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY JOHN D. POLSTRA AND CONTRIBUTORS ``AS IS'' AND 14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16 * ARE DISCLAIMED. IN NO EVENT SHALL JOHN D. POLSTRA OR CONTRIBUTORS BE LIABLE 17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23 * SUCH DAMAGE. 24 * 25 * $FreeBSD: src/usr.bin/lockf/lockf.c,v 1.8 1999/08/28 01:03:07 peter Exp $ 26 * $DragonFly: src/usr.bin/lockf/lockf.c,v 1.3 2005/01/05 00:46:52 cpressey Exp $ 27 */ 28 29 #include <sys/types.h> 30 #include <sys/wait.h> 31 32 #include <err.h> 33 #include <errno.h> 34 #include <fcntl.h> 35 #include <signal.h> 36 #include <stdio.h> 37 #include <stdlib.h> 38 #include <sysexits.h> 39 #include <unistd.h> 40 41 static int acquire_lock(const char *name); 42 static void cleanup(void); 43 static void killed(int sig); 44 static void timeout(int sig); 45 static void usage(void); 46 static void wait_for_lock(const char *name); 47 48 static const char *lockname; 49 static int lockfd; 50 static int keep; 51 static volatile sig_atomic_t timed_out; 52 53 /* 54 * Execute an arbitrary command while holding a file lock. 55 */ 56 int 57 main(int argc, char **argv) 58 { 59 int ch; 60 int silent; 61 int status; 62 int waitsec; 63 pid_t child; 64 65 silent = 0; 66 keep = 0; 67 waitsec = -1; /* Infinite. */ 68 while ((ch = getopt(argc, argv, "skt:")) != -1) { 69 switch (ch) { 70 71 case 'k': 72 keep = 1; 73 break; 74 75 case 's': 76 silent = 1; 77 break; 78 79 case 't': 80 { 81 char *endptr; 82 waitsec = strtol(optarg, &endptr, 0); 83 if (*optarg == '\0' || *endptr != '\0' || waitsec < 0) 84 errx(EX_USAGE, "invalid timeout \"%s\"", optarg); 85 } 86 break; 87 88 default: 89 usage(); 90 } 91 } 92 if (argc - optind < 2) 93 usage(); 94 lockname = argv[optind++]; 95 argc -= optind; 96 argv += optind; 97 98 if (waitsec > 0) { /* Set up a timeout. */ 99 struct sigaction act; 100 101 act.sa_handler = timeout; 102 sigemptyset(&act.sa_mask); 103 act.sa_flags = 0; /* Note that we do not set SA_RESTART. */ 104 105 sigaction(SIGALRM, &act, NULL); 106 alarm(waitsec); 107 } 108 109 lockfd = acquire_lock(lockname); 110 while (lockfd == -1 && !timed_out && waitsec != 0) { 111 wait_for_lock(lockname); 112 lockfd = acquire_lock(lockname); 113 } 114 115 if (waitsec > 0) 116 alarm(0); 117 118 if (lockfd == -1) { /* We failed to acquire the lock. */ 119 if (silent) 120 exit(EX_TEMPFAIL); 121 errx(EX_TEMPFAIL, "%s: already locked", lockname); 122 } 123 124 /* At this point, we own the lock. */ 125 126 if (atexit(cleanup) == -1) 127 err(EX_OSERR, "atexit failed"); 128 129 if ((child = fork()) == -1) 130 err(EX_OSERR, "cannot fork"); 131 132 if (child == 0) { /* The child process. */ 133 close(lockfd); 134 execvp(argv[0], argv); 135 perror(argv[0]); 136 _exit(1); 137 } 138 139 /* This is the parent process. */ 140 141 signal(SIGINT, SIG_IGN); 142 signal(SIGQUIT, SIG_IGN); 143 signal(SIGTERM, killed); 144 145 if (waitpid(child, &status, 0) == -1) 146 err(EX_OSERR, "waitpid failed"); 147 148 return WIFEXITED(status) ? WEXITSTATUS(status) : 1; 149 } 150 151 /* 152 * Try to acquire a lock on the given file, but don't wait for it. Returns 153 * an open file descriptor on success, or -1 on failure. 154 */ 155 static int 156 acquire_lock(const char *name) 157 { 158 int fd; 159 160 if ((fd = open(name, O_RDONLY|O_CREAT|O_EXLOCK|O_NONBLOCK, 0666)) == -1) { 161 if (errno == EAGAIN || errno == EINTR) 162 return -1; 163 err(EX_CANTCREAT, "cannot open %s", name); 164 } 165 return fd; 166 } 167 168 /* 169 * Remove the lock file. 170 */ 171 static void 172 cleanup(void) 173 { 174 if (keep) 175 flock(lockfd, LOCK_UN); 176 else 177 unlink(lockname); 178 } 179 180 /* 181 * Signal handler for SIGTERM. Cleans up the lock file, then re-raises 182 * the signal. 183 */ 184 static void 185 killed(int sig) 186 { 187 cleanup(); 188 signal(sig, SIG_DFL); 189 if (kill(getpid(), sig) == -1) 190 err(EX_OSERR, "kill failed"); 191 } 192 193 /* 194 * Signal handler for SIGALRM. 195 */ 196 static void 197 timeout(__unused int sig) 198 { 199 timed_out = 1; 200 } 201 202 static void 203 usage(void) 204 { 205 fprintf(stderr, 206 "usage: lockf [-ks] [-t seconds] file command [arguments]\n"); 207 exit(EX_USAGE); 208 } 209 210 /* 211 * Wait until it might be possible to acquire a lock on the given file. 212 */ 213 static void 214 wait_for_lock(const char *name) 215 { 216 int fd; 217 218 if ((fd = open(name, O_RDONLY|O_EXLOCK)) == -1) { 219 if (errno == ENOENT || errno == EINTR) 220 return; 221 err(EX_CANTCREAT, "cannot open %s", name); 222 } 223 close(fd); 224 return; 225 } 226