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
  46 static 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
  60 const char *program;
  61
  62 static 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
  83 static sig_atomic_t timeout_expired = 0;
  84
  85 static void timeout_handler(int sig)
  86 {
  87   (void)sig;
  88
  89   timeout_expired = 1;
  90 }
  91
  92
  93 static 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
 124 int 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