Root/tools/flock/src/flock.c

1/* ----------------------------------------------------------------------- *
2 *
3 * Copyright 2003-2005 H. Peter Anvin - All Rights Reserved
4 *
5 * Permission is hereby granted, free of charge, to any person
6 * obtaining a copy of this software and associated documentation
7 * files (the "Software"), to deal in the Software without
8 * restriction, including without limitation the rights to use,
9 * copy, modify, merge, publish, distribute, sublicense, and/or
10 * sell copies of the Software, and to permit persons to whom
11 * the Software is furnished to do so, subject to the following
12 * conditions:
13 *
14 * The above copyright notice and this permission notice shall
15 * be included in all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
19 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
20 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
21 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
22 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
23 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
24 * OTHER DEALINGS IN THE SOFTWARE.
25 *
26 * ----------------------------------------------------------------------- */
27
28#include <errno.h>
29#include <stdio.h>
30#include <stdlib.h>
31#include <unistd.h>
32#include <getopt.h>
33#include <signal.h>
34#include <ctype.h>
35#include <string.h>
36#include <paths.h>
37#include <sysexits.h>
38#include <sys/types.h>
39#include <sys/file.h>
40#include <sys/time.h>
41#include <sys/wait.h>
42
43#define PACKAGE_STRING "util-linux-ng 2.18"
44#define _(x) (x)
45
46static const struct option long_options[] = {
47  { "shared", 0, NULL, 's' },
48  { "exclusive", 0, NULL, 'x' },
49  { "unlock", 0, NULL, 'u' },
50  { "nonblocking", 0, NULL, 'n' },
51  { "nb", 0, NULL, 'n' },
52  { "timeout", 1, NULL, 'w' },
53  { "wait", 1, NULL, 'w' },
54  { "close", 0, NULL, 'o' },
55  { "help", 0, NULL, 'h' },
56  { "version", 0, NULL, 'V' },
57  { 0, 0, 0, 0 }
58};
59
60const char *program;
61
62static void usage(int ex)
63{
64  fputs("flock (" PACKAGE_STRING ")\n", stderr);
65  fprintf(stderr,
66    _("Usage: %1$s [-sxun][-w #] fd#\n"
67      " %1$s [-sxon][-w #] file [-c] command...\n"
68      " %1$s [-sxon][-w #] directory [-c] command...\n"
69      " -s --shared Get a shared lock\n"
70      " -x --exclusive Get an exclusive lock\n"
71      " -u --unlock Remove a lock\n"
72      " -n --nonblock Fail rather than wait\n"
73      " -w --timeout Wait for a limited amount of time\n"
74      " -o --close Close file descriptor before running command\n"
75      " -c --command Run a single command string through the shell\n"
76      " -h --help Display this text\n"
77      " -V --version Display version\n"),
78      program);
79  exit(ex);
80}
81
82
83static sig_atomic_t timeout_expired = 0;
84
85static void timeout_handler(int sig)
86{
87  (void)sig;
88
89  timeout_expired = 1;
90}
91
92
93static char * strtotimeval(const char *str, struct timeval *tv)
94{
95  char *s;
96  long fs; /* Fractional seconds */
97  int i;
98
99  tv->tv_sec = strtol(str, &s, 10);
100  fs = 0;
101
102  if ( *s == '.' ) {
103    s++;
104
105    for ( i = 0 ; i < 6 ; i++ ) {
106      if ( !isdigit(*s) )
107    break;
108
109      fs *= 10;
110      fs += *s++ - '0';
111    }
112
113    for ( ; i < 6; i++ )
114      fs *= 10;
115
116    while ( isdigit(*s) )
117      s++;
118  }
119
120  tv->tv_usec = fs;
121  return s;
122}
123
124int main(int argc, char *argv[])
125{
126  struct itimerval timeout, old_timer;
127  int have_timeout = 0;
128  int type = LOCK_EX;
129  int block = 0;
130  int fd = -1;
131  int opt, ix;
132  int do_close = 0;
133  int err;
134  int status;
135  char *eon;
136  char **cmd_argv = NULL, *sh_c_argv[4];
137  const char *filename = NULL;
138  struct sigaction sa, old_sa;
139
140  program = argv[0];
141
142  if ( argc < 2 )
143    usage(EX_USAGE);
144
145  memset(&timeout, 0, sizeof timeout);
146
147  optopt = 0;
148  while ( (opt = getopt_long(argc, argv, "+sexnouw:hV?", long_options, &ix)) != EOF ) {
149    switch(opt) {
150    case 's':
151      type = LOCK_SH;
152      break;
153    case 'e':
154    case 'x':
155      type = LOCK_EX;
156      break;
157    case 'u':
158      type = LOCK_UN;
159      break;
160    case 'o':
161      do_close = 1;
162      break;
163    case 'n':
164      block = LOCK_NB;
165      break;
166    case 'w':
167      have_timeout = 1;
168      eon = strtotimeval(optarg, &timeout.it_value);
169      if ( *eon )
170    usage(EX_USAGE);
171      break;
172    case 'V':
173      printf("flock (%s)\n", PACKAGE_STRING);
174      exit(0);
175    default:
176      /* optopt will be set if this was an unrecognized option, i.e. *not* 'h' or '?' */
177      usage(optopt ? EX_USAGE : 0);
178      break;
179    }
180  }
181
182  if ( argc > optind+1 ) {
183    /* Run command */
184
185    if ( !strcmp(argv[optind+1], "-c") ||
186     !strcmp(argv[optind+1], "--command") ) {
187
188      if ( argc != optind+3 ) {
189    fprintf(stderr, _("%s: %s requires exactly one command argument\n"),
190        program, argv[optind+1]);
191    exit(EX_USAGE);
192      }
193
194      cmd_argv = sh_c_argv;
195
196      cmd_argv[0] = getenv("SHELL");
197      if ( !cmd_argv[0] || !*cmd_argv[0] )
198    cmd_argv[0] = _PATH_BSHELL;
199
200      cmd_argv[1] = "-c";
201      cmd_argv[2] = argv[optind+2];
202      cmd_argv[3] = 0;
203    } else {
204      cmd_argv = &argv[optind+1];
205    }
206
207    filename = argv[optind];
208    fd = open(filename, O_RDONLY|O_NOCTTY|O_CREAT, 0666);
209    /* Linux doesn't like O_CREAT on a directory, even though it should be a
210       no-op */
211    if (fd < 0 && errno == EISDIR)
212        fd = open(filename, O_RDONLY|O_NOCTTY);
213
214    if ( fd < 0 ) {
215      err = errno;
216      fprintf(stderr, _("%s: cannot open lock file %s: %s\n"),
217          program, argv[optind], strerror(err));
218      exit((err == ENOMEM||err == EMFILE||err == ENFILE) ? EX_OSERR :
219       (err == EROFS||err == ENOSPC) ? EX_CANTCREAT :
220       EX_NOINPUT);
221    }
222
223  } else if (optind < argc) {
224    /* Use provided file descriptor */
225
226    fd = (int)strtol(argv[optind], &eon, 10);
227    if ( *eon || !argv[optind] ) {
228      fprintf(stderr, _("%s: bad number: %s\n"), program, argv[optind]);
229      exit(EX_USAGE);
230    }
231
232  } else {
233    /* Bad options */
234
235    fprintf(stderr, _("%s: requires file descriptor, file or directory\n"),
236        program);
237    exit(EX_USAGE);
238  }
239
240
241  if ( have_timeout ) {
242    if ( timeout.it_value.tv_sec == 0 &&
243     timeout.it_value.tv_usec == 0 ) {
244      /* -w 0 is equivalent to -n; this has to be special-cased
245     because setting an itimer to zero means disabled! */
246
247      have_timeout = 0;
248      block = LOCK_NB;
249    } else {
250      memset(&sa, 0, sizeof sa);
251
252      sa.sa_handler = timeout_handler;
253      sa.sa_flags = SA_RESETHAND;
254      sigaction(SIGALRM, &sa, &old_sa);
255
256      setitimer(ITIMER_REAL, &timeout, &old_timer);
257    }
258  }
259
260  while ( flock(fd, type|block) ) {
261    switch( (err = errno) ) {
262    case EWOULDBLOCK: /* -n option set and failed to lock */
263      exit(1);
264    case EINTR: /* Signal received */
265      if ( timeout_expired )
266    exit(1); /* -w option set and failed to lock */
267      continue; /* otherwise try again */
268    default: /* Other errors */
269      if ( filename )
270    fprintf(stderr, "%s: %s: %s\n", program, filename, strerror(err));
271      else
272    fprintf(stderr, "%s: %d: %s\n", program, fd, strerror(err));
273      exit((err == ENOLCK||err == ENOMEM) ? EX_OSERR : EX_DATAERR);
274    }
275  }
276
277  if ( have_timeout ) {
278    setitimer(ITIMER_REAL, &old_timer, NULL); /* Cancel itimer */
279    sigaction(SIGALRM, &old_sa, NULL); /* Cancel signal handler */
280  }
281
282  status = 0;
283
284  if ( cmd_argv ) {
285    pid_t w, f;
286
287    /* Clear any inherited settings */
288    signal(SIGCHLD, SIG_DFL);
289    f = fork();
290
291    if ( f < 0 ) {
292      err = errno;
293      fprintf(stderr, _("%s: fork failed: %s\n"), program, strerror(err));
294      exit(EX_OSERR);
295    } else if ( f == 0 ) {
296      if ( do_close )
297    close(fd);
298      err = errno;
299      execvp(cmd_argv[0], cmd_argv);
300      /* execvp() failed */
301      fprintf(stderr, "%s: %s: %s\n", program, cmd_argv[0], strerror(err));
302      _exit((err == ENOMEM) ? EX_OSERR: EX_UNAVAILABLE);
303    } else {
304      do {
305    w = waitpid(f, &status, 0);
306    if (w == -1 && errno != EINTR)
307      break;
308      } while ( w != f );
309
310      if (w == -1) {
311    err = errno;
312    status = EXIT_FAILURE;
313    fprintf(stderr, "%s: waitpid failed: %s\n", program, strerror(err));
314      } else if ( WIFEXITED(status) )
315    status = WEXITSTATUS(status);
316      else if ( WIFSIGNALED(status) )
317    status = WTERMSIG(status) + 128;
318      else
319    status = EX_OSERR; /* WTF? */
320    }
321  }
322
323  return status;
324}
325
326

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