1 // From https://github.com/magnumripper/fcntl-lock
2 // SPDX-License-Identifier: MIT
3 /* ----------------------------------------------------------------------- *
4 *
5 * Copyright 2003-2005 H. Peter Anvin - All Rights Reserved
6 * Copyright 2015 magnum (fcntl version)
7 *
8 * Permission is hereby granted, free of charge, to any person
9 * obtaining a copy of this software and associated documentation
10 * files (the "Software"), to deal in the Software without
11 * restriction, including without limitation the rights to use,
12 * copy, modify, merge, publish, distribute, sublicense, and/or
13 * sell copies of the Software, and to permit persons to whom
14 * the Software is furnished to do so, subject to the following
15 * conditions:
16 *
17 * The above copyright notice and this permission notice shall
18 * be included in all copies or substantial portions of the Software.
19 *
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
22 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
24 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
25 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
26 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
27 * OTHER DEALINGS IN THE SOFTWARE.
28 *
29 * ----------------------------------------------------------------------- */
30
31 #include <errno.h>
32 #include <stdio.h>
33 #include <stdlib.h>
34 #include <fcntl.h>
35 #include <unistd.h>
36 #include <getopt.h>
37 #include <signal.h>
38 #include <ctype.h>
39 #include <string.h>
40 #include <paths.h>
41 #include <sysexits.h>
42 #include <sys/types.h>
43 #include <sys/file.h>
44 #include <sys/time.h>
45 #include <sys/wait.h>
46
47 #define PACKAGE_STRING "magnum"
48 #define _(x) (x)
49
50 static const struct option long_options[] = {
51 { "shared", 0, NULL, 's' },
52 { "exclusive", 0, NULL, 'x' },
53 { "unlock", 0, NULL, 'u' },
54 { "nonblocking", 0, NULL, 'n' },
55 { "nb", 0, NULL, 'n' },
56 { "timeout", 1, NULL, 'w' },
57 { "wait", 1, NULL, 'w' },
58 { "close", 0, NULL, 'o' },
59 { "help", 0, NULL, 'h' },
60 { "version", 0, NULL, 'V' },
61 { 0, 0, 0, 0 }
62 };
63
64 const char *program;
65
usage(int ex)66 static void usage(int ex)
67 {
68 fputs("fcntl-lock (" PACKAGE_STRING ")\n", stderr);
69 fprintf(stderr,
70 _("Usage: %1$s [-sxun][-w #] fd#\n"
71 " %1$s [-sxon][-w #] file [-c] command...\n"
72 " %1$s [-sxon][-w #] directory [-c] command...\n"
73 " -s --shared Get a shared lock\n"
74 " -x --exclusive Get an exclusive lock\n"
75 " -u --unlock Remove a lock\n"
76 " -n --nonblock Fail rather than wait\n"
77 " -w --timeout Wait for a limited amount of time\n"
78 " -o --close Close file descriptor before running command\n"
79 " -c --command Run a single command string through the shell\n"
80 " -h --help Display this text\n"
81 " -V --version Display version\n"),
82 program);
83 exit(ex);
84 }
85
86
87 static sig_atomic_t timeout_expired = 0;
88
timeout_handler(int sig)89 static void timeout_handler(int sig)
90 {
91 (void)sig;
92
93 timeout_expired = 1;
94 }
95
96
strtotimeval(const char * str,struct timeval * tv)97 static char * strtotimeval(const char *str, struct timeval *tv)
98 {
99 char *s;
100 long fs; /* Fractional seconds */
101 int i;
102
103 tv->tv_sec = strtol(str, &s, 10);
104 fs = 0;
105
106 if ( *s == '.' ) {
107 s++;
108
109 for ( i = 0 ; i < 6 ; i++ ) {
110 if ( !isdigit(*s) )
111 break;
112
113 fs *= 10;
114 fs += *s++ - '0';
115 }
116
117 for ( ; i < 6; i++ )
118 fs *= 10;
119
120 while ( isdigit(*s) )
121 s++;
122 }
123
124 tv->tv_usec = fs;
125 return s;
126 }
127
main(int argc,char * argv[])128 int main(int argc, char *argv[])
129 {
130 struct itimerval timeout, old_timer;
131 int have_timeout = 0;
132 int type = F_WRLCK;
133 int block = F_SETLKW;
134 int fd = -1;
135 int opt, ix;
136 int do_close = 0;
137 int err;
138 int status;
139 char *eon;
140 char **cmd_argv = NULL, *sh_c_argv[4];
141 struct flock lock;
142 const char *filename = NULL;
143 struct sigaction sa, old_sa;
144
145 program = argv[0];
146
147 if ( argc < 2 )
148 usage(EX_USAGE);
149
150 memset(&timeout, 0, sizeof timeout);
151
152 optopt = 0;
153 while ( (opt = getopt_long(argc, argv, "+sexnouw:hV?", long_options, &ix)) != EOF ) {
154 switch(opt) {
155 case 's':
156 type = F_RDLCK;
157 break;
158 case 'e':
159 case 'x':
160 type = F_WRLCK;
161 break;
162 case 'u':
163 type = F_UNLCK;
164 break;
165 case 'o':
166 do_close = 1;
167 break;
168 case 'n':
169 block = F_SETLK;
170 break;
171 case 'w':
172 have_timeout = 1;
173 eon = strtotimeval(optarg, &timeout.it_value);
174 if ( *eon )
175 usage(EX_USAGE);
176 break;
177 case 'V':
178 printf("fcntl-lock (%s)\n", PACKAGE_STRING);
179 exit(0);
180 default:
181 /* optopt will be set if this was an unrecognized option, i.e. *not* 'h' or '?' */
182 usage(optopt ? EX_USAGE : 0);
183 break;
184 }
185 }
186
187 if ( argc > optind+1 ) {
188 /* Run command */
189
190 if ( !strcmp(argv[optind+1], "-c") ||
191 !strcmp(argv[optind+1], "--command") ) {
192
193 if ( argc != optind+3 ) {
194 fprintf(stderr, _("%s: %s requires exactly one command argument\n"),
195 program, argv[optind+1]);
196 exit(EX_USAGE);
197 }
198
199 cmd_argv = sh_c_argv;
200
201 cmd_argv[0] = getenv("SHELL");
202 if ( !cmd_argv[0] || !*cmd_argv[0] )
203 cmd_argv[0] = _PATH_BSHELL;
204
205 cmd_argv[1] = "-c";
206 cmd_argv[2] = argv[optind+2];
207 cmd_argv[3] = 0;
208 } else {
209 cmd_argv = &argv[optind+1];
210 }
211
212 filename = argv[optind];
213 fd = open(filename, O_RDWR|O_NOCTTY|O_CREAT, 0666);
214 /* Linux doesn't like O_CREAT on a directory, even though it should be a
215 no-op */
216 if (fd < 0 && errno == EISDIR)
217 fd = open(filename, O_RDONLY|O_NOCTTY);
218
219 if ( fd < 0 ) {
220 err = errno;
221 fprintf(stderr, _("%s: cannot open lock file %s: %s\n"),
222 program, argv[optind], strerror(err));
223 exit((err == ENOMEM||err == EMFILE||err == ENFILE) ? EX_OSERR :
224 (err == EROFS||err == ENOSPC) ? EX_CANTCREAT :
225 EX_NOINPUT);
226 }
227
228 } else if (optind < argc) {
229 /* Use provided file descriptor */
230
231 fd = (int)strtol(argv[optind], &eon, 10);
232 if ( *eon || !argv[optind] ) {
233 fprintf(stderr, _("%s: bad number: %s\n"), program, argv[optind]);
234 exit(EX_USAGE);
235 }
236
237 } else {
238 /* Bad options */
239
240 fprintf(stderr, _("%s: requires file descriptor, file or directory\n"),
241 program);
242 exit(EX_USAGE);
243 }
244
245
246 if ( have_timeout ) {
247 if ( timeout.it_value.tv_sec == 0 &&
248 timeout.it_value.tv_usec == 0 ) {
249 /* -w 0 is equivalent to -n; this has to be special-cased
250 because setting an itimer to zero means disabled! */
251
252 have_timeout = 0;
253 block = F_SETLK;
254 } else {
255 memset(&sa, 0, sizeof sa);
256
257 sa.sa_handler = timeout_handler;
258 sa.sa_flags = SA_RESETHAND;
259 sigaction(SIGALRM, &sa, &old_sa);
260
261 setitimer(ITIMER_REAL, &timeout, &old_timer);
262 }
263 }
264
265 memset(&lock, 0, sizeof(lock));
266 lock.l_type = type;
267 while ( fcntl(fd, block, &lock) ) {
268 switch( (err = errno) ) {
269 case EAGAIN: /* -n option set and failed to lock */
270 case EACCES: /* -n option set and failed to lock */
271 exit(1);
272 case EINTR: /* Signal received */
273 if ( timeout_expired )
274 exit(1); /* -w option set and failed to lock */
275 continue; /* otherwise try again */
276 default: /* Other errors */
277 if ( filename )
278 fprintf(stderr, "%s: %s: %s\n", program, filename, strerror(err));
279 else
280 fprintf(stderr, "%s: %d: %s\n", program, fd, strerror(err));
281 exit((err == ENOLCK||err == ENOMEM) ? EX_OSERR : EX_DATAERR);
282 }
283 }
284
285 if ( have_timeout ) {
286 setitimer(ITIMER_REAL, &old_timer, NULL); /* Cancel itimer */
287 sigaction(SIGALRM, &old_sa, NULL); /* Cancel signal handler */
288 }
289
290 status = 0;
291
292 if ( cmd_argv ) {
293 pid_t w, f;
294
295 /* Clear any inherited settings */
296 signal(SIGCHLD, SIG_DFL);
297 f = fork();
298
299 if ( f < 0 ) {
300 err = errno;
301 fprintf(stderr, _("%s: fork failed: %s\n"), program, strerror(err));
302 exit(EX_OSERR);
303 } else if ( f == 0 ) {
304 if ( do_close )
305 close(fd);
306 err = errno;
307 execvp(cmd_argv[0], cmd_argv);
308 /* execvp() failed */
309 fprintf(stderr, "%s: %s: %s\n", program, cmd_argv[0], strerror(err));
310 _exit((err == ENOMEM) ? EX_OSERR: EX_UNAVAILABLE);
311 } else {
312 do {
313 w = waitpid(f, &status, 0);
314 if (w == -1 && errno != EINTR)
315 break;
316 } while ( w != f );
317
318 if (w == -1) {
319 err = errno;
320 status = EXIT_FAILURE;
321 fprintf(stderr, "%s: waitpid failed: %s\n", program, strerror(err));
322 } else if ( WIFEXITED(status) )
323 status = WEXITSTATUS(status);
324 else if ( WIFSIGNALED(status) )
325 status = WTERMSIG(status) + 128;
326 else
327 status = EX_OSERR; /* WTF? */
328 }
329 }
330
331 return status;
332 }
333