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 #include <fcntl.h>
  43
  44 #define PACKAGE_STRING "util-linux-ng 2.18"
  45 #define _(x) (x)
  46
  47 static const struct option long_options[] = {
  48   { "shared",       0, NULL, 's' },
  49   { "exclusive",    0, NULL, 'x' },
  50   { "unlock",       0, NULL, 'u' },
  51   { "nonblocking",  0, NULL, 'n' },
  52   { "nb",           0, NULL, 'n' },
  53   { "timeout",      1, NULL, 'w' },
  54   { "wait",         1, NULL, 'w' },
  55   { "close",        0, NULL, 'o' },
  56   { "help",         0, NULL, 'h' },
  57   { "version",      0, NULL, 'V' },
  58   { 0, 0, 0, 0 }
  59 };
  60
  61 const char *program;
  62
  63 static void usage(int ex)
  64 {
  65   fputs("flock (" PACKAGE_STRING ")\n", stderr);
  66   fprintf(stderr,
  67         _("Usage: %1$s [-sxun][-w #] fd#\n"
  68           "       %1$s [-sxon][-w #] file [-c] command...\n"
  69           "       %1$s [-sxon][-w #] directory [-c] command...\n"
  70           "  -s  --shared     Get a shared lock\n"
  71           "  -x  --exclusive  Get an exclusive lock\n"
  72           "  -u  --unlock     Remove a lock\n"
  73           "  -n  --nonblock   Fail rather than wait\n"
  74           "  -w  --timeout    Wait for a limited amount of time\n"
  75           "  -o  --close      Close file descriptor before running command\n"
  76           "  -c  --command    Run a single command string through the shell\n"
  77           "  -h  --help       Display this text\n"
  78           "  -V  --version    Display version\n"),
  79           program);
  80   exit(ex);
  81 }
  82
  83
  84 static sig_atomic_t timeout_expired = 0;
  85
  86 static void timeout_handler(int sig)
  87 {
  88   (void)sig;
  89
  90   timeout_expired = 1;
  91 }
  92
  93
  94 static char * strtotimeval(const char *str, struct timeval *tv)
  95 {
  96   char *s;
  97   long fs;                      /* Fractional seconds */
  98   int i;
  99
 100   tv->tv_sec = strtol(str, &s, 10);
 101   fs = 0;
 102
 103   if ( *s == '.' ) {
 104     s++;
 105
 106     for ( i = 0 ; i < 6 ; i++ ) {
 107       if ( !isdigit(*s) )
 108         break;
 109
 110       fs *= 10;
 111       fs += *s++ - '0';
 112     }
 113
 114     for ( ; i < 6; i++ )
 115       fs *= 10;
 116
 117     while ( isdigit(*s) )
 118       s++;
 119   }
 120
 121   tv->tv_usec = fs;
 122   return s;
 123 }
 124
 125 int main(int argc, char *argv[])
 126 {
 127   struct itimerval timeout, old_timer;
 128   int have_timeout = 0;
 129   int type = LOCK_EX;
 130   int block = 0;
 131   int fd = -1;
 132   int opt, ix;
 133   int do_close = 0;
 134   int err;
 135   int status;
 136   int open_flags = 0;
 137   char *eon;
 138   char **cmd_argv = NULL, *sh_c_argv[4];
 139   const char *filename = NULL;
 140   struct sigaction sa, old_sa;
 141
 142   program = argv[0];
 143
 144   if ( argc < 2 )
 145     usage(EX_USAGE);
 146
 147   memset(&timeout, 0, sizeof timeout);
 148
 149   optopt = 0;
 150   while ( (opt = getopt_long(argc, argv, "+sexnouw:hV?", long_options, &ix)) != EOF ) {
 151     switch(opt) {
 152     case 's':
 153       type = LOCK_SH;
 154       break;
 155     case 'e':
 156     case 'x':
 157       type = LOCK_EX;
 158       break;
 159     case 'u':
 160       type = LOCK_UN;
 161       break;
 162     case 'o':
 163       do_close = 1;
 164       break;
 165     case 'n':
 166       block = LOCK_NB;
 167       break;
 168     case 'w':
 169       have_timeout = 1;
 170       eon = strtotimeval(optarg, &timeout.it_value);
 171       if ( *eon )
 172         usage(EX_USAGE);
 173       break;
 174     case 'V':
 175       printf("flock (%s)\n", PACKAGE_STRING);
 176       exit(0);
 177     default:
 178       /* optopt will be set if this was an unrecognized option, i.e. *not* 'h' or '?' */
 179       usage(optopt ? EX_USAGE : 0);
 180       break;
 181     }
 182   }
 183
 184   if ( argc > optind+1 ) {
 185     /* Run command */
 186
 187     if ( !strcmp(argv[optind+1], "-c") ||
 188          !strcmp(argv[optind+1], "--command") ) {
 189
 190       if ( argc != optind+3 ) {
 191         fprintf(stderr, _("%s: %s requires exactly one command argument\n"),
 192                 program, argv[optind+1]);
 193         exit(EX_USAGE);
 194       }
 195
 196       cmd_argv = sh_c_argv;
 197
 198       cmd_argv[0] = getenv("SHELL");
 199       if ( !cmd_argv[0] || !*cmd_argv[0] )
 200         cmd_argv[0] = _PATH_BSHELL;
 201
 202       cmd_argv[1] = "-c";
 203       cmd_argv[2] = argv[optind+2];
 204       cmd_argv[3] = 0;
 205     } else {
 206       cmd_argv = &argv[optind+1];
 207     }
 208
 209     filename = argv[optind];
 210     fd = open(filename, O_RDONLY|O_NOCTTY|O_CREAT, 0666);
 211     /* Linux doesn't like O_CREAT on a directory, even though it should be a
 212        no-op */
 213     if (fd < 0 && errno == EISDIR)
 214         fd = open(filename, O_RDONLY|O_NOCTTY);
 215
 216     if ( fd < 0 ) {
 217       err = errno;
 218       fprintf(stderr, _("%s: cannot open lock file %s: %s\n"),
 219               program, argv[optind], strerror(err));
 220       exit((err == ENOMEM||err == EMFILE||err == ENFILE) ? EX_OSERR :
 221            (err == EROFS||err == ENOSPC) ? EX_CANTCREAT :
 222            EX_NOINPUT);
 223     }
 224
 225   } else if (optind < argc) {
 226     /* Use provided file descriptor */
 227
 228     fd = (int)strtol(argv[optind], &eon, 10);
 229     if ( *eon || !argv[optind] ) {
 230       fprintf(stderr, _("%s: bad number: %s\n"), program, argv[optind]);
 231       exit(EX_USAGE);
 232     }
 233
 234   } else {
 235     /* Bad options */
 236
 237     fprintf(stderr, _("%s: requires file descriptor, file or directory\n"),
 238                 program);
 239     exit(EX_USAGE);
 240   }
 241
 242
 243   if ( have_timeout ) {
 244     if ( timeout.it_value.tv_sec == 0 &&
 245          timeout.it_value.tv_usec == 0 ) {
 246       /* -w 0 is equivalent to -n; this has to be special-cased
 247          because setting an itimer to zero means disabled! */
 248
 249       have_timeout = 0;
 250       block = LOCK_NB;
 251     } else {
 252       memset(&sa, 0, sizeof sa);
 253
 254       sa.sa_handler = timeout_handler;
 255       sa.sa_flags   = SA_RESETHAND;
 256       sigaction(SIGALRM, &sa, &old_sa);
 257
 258       setitimer(ITIMER_REAL, &timeout, &old_timer);
 259     }
 260   }
 261
 262   while ( flock(fd, type|block) ) {
 263     switch( (err = errno) ) {
 264     case EWOULDBLOCK:           /* -n option set and failed to lock */
 265       exit(1);
 266     case EINTR:                 /* Signal received */
 267       if ( timeout_expired )
 268         exit(1);                /* -w option set and failed to lock */
 269       continue;                 /* otherwise try again */
 270     case EBADF:                 /* since Linux 3.4 (commit 55725513) */
 271       /* Probably NFSv4 where flock() is emulated by fcntl().
 272        * Let's try to reopen in read-write mode.
 273        */
 274       if (!(open_flags & O_RDWR) &&
 275           type != LOCK_SH &&
 276           filename &&
 277           access(filename, R_OK | W_OK) == 0) {
 278
 279               close(fd);
 280               open_flags = O_RDWR;
 281               fd = open(filename, open_flags);
 282               break;
 283       }
 284       /* go through */
 285     default:                    /* Other errors */
 286       if ( filename )
 287         fprintf(stderr, "%s: %s: %s\n", program, filename, strerror(err));
 288       else
 289         fprintf(stderr, "%s: %d: %s\n", program, fd, strerror(err));
 290       exit((err == ENOLCK||err == ENOMEM) ? EX_OSERR : EX_DATAERR);
 291     }
 292   }
 293
 294   if ( have_timeout ) {
 295     setitimer(ITIMER_REAL, &old_timer, NULL); /* Cancel itimer */
 296     sigaction(SIGALRM, &old_sa, NULL); /* Cancel signal handler */
 297   }
 298
 299   status = 0;
 300
 301   if ( cmd_argv ) {
 302     pid_t w, f;
 303
 304     /* Clear any inherited settings */
 305     signal(SIGCHLD, SIG_DFL);
 306     f = fork();
 307
 308     if ( f < 0 ) {
 309       err = errno;
 310       fprintf(stderr, _("%s: fork failed: %s\n"), program, strerror(err));
 311       exit(EX_OSERR);
 312     } else if ( f == 0 ) {
 313       if ( do_close )
 314         close(fd);
 315       err = errno;
 316       execvp(cmd_argv[0], cmd_argv);
 317       /* execvp() failed */
 318       fprintf(stderr, "%s: %s: %s\n", program, cmd_argv[0], strerror(err));
 319       _exit((err == ENOMEM) ? EX_OSERR: EX_UNAVAILABLE);
 320     } else {
 321       do {
 322         w = waitpid(f, &status, 0);
 323         if (w == -1 && errno != EINTR)
 324           break;
 325       } while ( w != f );
 326
 327       if (w == -1) {
 328         err = errno;
 329         status = EXIT_FAILURE;
 330         fprintf(stderr, "%s: waitpid failed: %s\n", program, strerror(err));
 331       } else if ( WIFEXITED(status) )
 332         status = WEXITSTATUS(status);
 333       else if ( WIFSIGNALED(status) )
 334         status = WTERMSIG(status) + 128;
 335       else
 336         status = EX_OSERR;      /* WTF? */
 337     }
 338   }
 339
 340   return status;
 341 }
 342