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   char *eon;
 137   char **cmd_argv = NULL, *sh_c_argv[4];
 138   const char *filename = NULL;
 139   struct sigaction sa, old_sa;
 140
 141   program = argv[0];
 142
 143   if ( argc < 2 )
 144     usage(EX_USAGE);
 145
 146   memset(&timeout, 0, sizeof timeout);
 147
 148   optopt = 0;
 149   while ( (opt = getopt_long(argc, argv, "+sexnouw:hV?", long_options, &ix)) != EOF ) {
 150     switch(opt) {
 151     case 's':
 152       type = LOCK_SH;
 153       break;
 154     case 'e':
 155     case 'x':
 156       type = LOCK_EX;
 157       break;
 158     case 'u':
 159       type = LOCK_UN;
 160       break;
 161     case 'o':
 162       do_close = 1;
 163       break;
 164     case 'n':
 165       block = LOCK_NB;
 166       break;
 167     case 'w':
 168       have_timeout = 1;
 169       eon = strtotimeval(optarg, &timeout.it_value);
 170       if ( *eon )
 171         usage(EX_USAGE);
 172       break;
 173     case 'V':
 174       printf("flock (%s)\n", PACKAGE_STRING);
 175       exit(0);
 176     default:
 177       /* optopt will be set if this was an unrecognized option, i.e. *not* 'h' or '?' */
 178       usage(optopt ? EX_USAGE : 0);
 179       break;
 180     }
 181   }
 182
 183   if ( argc > optind+1 ) {
 184     /* Run command */
 185
 186     if ( !strcmp(argv[optind+1], "-c") ||
 187          !strcmp(argv[optind+1], "--command") ) {
 188
 189       if ( argc != optind+3 ) {
 190         fprintf(stderr, _("%s: %s requires exactly one command argument\n"),
 191                 program, argv[optind+1]);
 192         exit(EX_USAGE);
 193       }
 194
 195       cmd_argv = sh_c_argv;
 196
 197       cmd_argv[0] = getenv("SHELL");
 198       if ( !cmd_argv[0] || !*cmd_argv[0] )
 199         cmd_argv[0] = _PATH_BSHELL;
 200
 201       cmd_argv[1] = "-c";
 202       cmd_argv[2] = argv[optind+2];
 203       cmd_argv[3] = 0;
 204     } else {
 205       cmd_argv = &argv[optind+1];
 206     }
 207
 208     filename = argv[optind];
 209     fd = open(filename, O_RDONLY|O_NOCTTY|O_CREAT, 0666);
 210     /* Linux doesn't like O_CREAT on a directory, even though it should be a
 211        no-op */
 212     if (fd < 0 && errno == EISDIR)
 213         fd = open(filename, O_RDONLY|O_NOCTTY);
 214
 215     if ( fd < 0 ) {
 216       err = errno;
 217       fprintf(stderr, _("%s: cannot open lock file %s: %s\n"),
 218               program, argv[optind], strerror(err));
 219       exit((err == ENOMEM||err == EMFILE||err == ENFILE) ? EX_OSERR :
 220            (err == EROFS||err == ENOSPC) ? EX_CANTCREAT :
 221            EX_NOINPUT);
 222     }
 223
 224   } else if (optind < argc) {
 225     /* Use provided file descriptor */
 226
 227     fd = (int)strtol(argv[optind], &eon, 10);
 228     if ( *eon || !argv[optind] ) {
 229       fprintf(stderr, _("%s: bad number: %s\n"), program, argv[optind]);
 230       exit(EX_USAGE);
 231     }
 232
 233   } else {
 234     /* Bad options */
 235
 236     fprintf(stderr, _("%s: requires file descriptor, file or directory\n"),
 237                 program);
 238     exit(EX_USAGE);
 239   }
 240
 241
 242   if ( have_timeout ) {
 243     if ( timeout.it_value.tv_sec == 0 &&
 244          timeout.it_value.tv_usec == 0 ) {
 245       /* -w 0 is equivalent to -n; this has to be special-cased
 246          because setting an itimer to zero means disabled! */
 247
 248       have_timeout = 0;
 249       block = LOCK_NB;
 250     } else {
 251       memset(&sa, 0, sizeof sa);
 252
 253       sa.sa_handler = timeout_handler;
 254       sa.sa_flags   = SA_RESETHAND;
 255       sigaction(SIGALRM, &sa, &old_sa);
 256
 257       setitimer(ITIMER_REAL, &timeout, &old_timer);
 258     }
 259   }
 260
 261   while ( flock(fd, type|block) ) {
 262     switch( (err = errno) ) {
 263     case EWOULDBLOCK:           /* -n option set and failed to lock */
 264       exit(1);
 265     case EINTR:                 /* Signal received */
 266       if ( timeout_expired )
 267         exit(1);                /* -w option set and failed to lock */
 268       continue;                 /* otherwise try again */
 269     default:                    /* Other errors */
 270       if ( filename )
 271         fprintf(stderr, "%s: %s: %s\n", program, filename, strerror(err));
 272       else
 273         fprintf(stderr, "%s: %d: %s\n", program, fd, strerror(err));
 274       exit((err == ENOLCK||err == ENOMEM) ? EX_OSERR : EX_DATAERR);
 275     }
 276   }
 277
 278   if ( have_timeout ) {
 279     setitimer(ITIMER_REAL, &old_timer, NULL); /* Cancel itimer */
 280     sigaction(SIGALRM, &old_sa, NULL); /* Cancel signal handler */
 281   }
 282
 283   status = 0;
 284
 285   if ( cmd_argv ) {
 286     pid_t w, f;
 287
 288     /* Clear any inherited settings */
 289     signal(SIGCHLD, SIG_DFL);
 290     f = fork();
 291
 292     if ( f < 0 ) {
 293       err = errno;
 294       fprintf(stderr, _("%s: fork failed: %s\n"), program, strerror(err));
 295       exit(EX_OSERR);
 296     } else if ( f == 0 ) {
 297       if ( do_close )
 298         close(fd);
 299       err = errno;
 300       execvp(cmd_argv[0], cmd_argv);
 301       /* execvp() failed */
 302       fprintf(stderr, "%s: %s: %s\n", program, cmd_argv[0], strerror(err));
 303       _exit((err == ENOMEM) ? EX_OSERR: EX_UNAVAILABLE);
 304     } else {
 305       do {
 306         w = waitpid(f, &status, 0);
 307         if (w == -1 && errno != EINTR)
 308           break;
 309       } while ( w != f );
 310
 311       if (w == -1) {
 312         err = errno;
 313         status = EXIT_FAILURE;
 314         fprintf(stderr, "%s: waitpid failed: %s\n", program, strerror(err));
 315       } else if ( WIFEXITED(status) )
 316         status = WEXITSTATUS(status);
 317       else if ( WIFSIGNALED(status) )
 318         status = WTERMSIG(status) + 128;
 319       else
 320         status = EX_OSERR;      /* WTF? */
 321     }
 322   }
 323
 324   return status;
 325 }
 326