release/src/router/busybox/util-linux/flock.c

   1 /*
   2  * Copyright (C) 2010 Timo Teras <timo.teras@iki.fi>
   3  *
   4  * This is free software, licensed under the GNU General Public License v2.
   5  */
   6
   7 //usage:#define flock_trivial_usage
   8 //usage:       "[-sxun] FD|{FILE [-c] PROG ARGS}"
   9 //usage:#define flock_full_usage "\n\n"
  10 //usage:       "[Un]lock file descriptor, or lock FILE, run PROG\n"
  11 //usage:     "\n        -s      Shared lock"
  12 //usage:     "\n        -x      Exclusive lock (default)"
  13 //usage:     "\n        -u      Unlock FD"
  14 //usage:     "\n        -n      Fail rather than wait"
  15
  16 #include <sys/file.h>
  17 #include "libbb.h"
  18
  19 int flock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  20 int flock_main(int argc UNUSED_PARAM, char **argv)
  21 {
  22         int mode, opt, fd;
  23         enum {
  24                 OPT_s = (1 << 0),
  25                 OPT_x = (1 << 1),
  26                 OPT_n = (1 << 2),
  27                 OPT_u = (1 << 3),
  28                 OPT_c = (1 << 4),
  29         };
  30
  31 #if ENABLE_LONG_OPTS
  32         static const char getopt_longopts[] ALIGN1 =
  33                 "shared\0"      No_argument       "s"
  34                 "exclusive\0"   No_argument       "x"
  35                 "unlock\0"      No_argument       "u"
  36                 "nonblock\0"    No_argument       "n"
  37                 ;
  38         applet_long_options = getopt_longopts;
  39 #endif
  40         opt_complementary = "-1";
  41
  42         opt = getopt32(argv, "+sxnu");
  43         argv += optind;
  44
  45         if (argv[1]) {
  46                 fd = open(argv[0], O_RDONLY|O_NOCTTY|O_CREAT, 0666);
  47                 if (fd < 0 && errno == EISDIR)
  48                         fd = open(argv[0], O_RDONLY|O_NOCTTY);
  49                 if (fd < 0)
  50                         bb_perror_msg_and_die("can't open '%s'", argv[0]);
  51                 //TODO? close_on_exec_on(fd);
  52         } else {
  53                 fd = xatoi_positive(argv[0]);
  54         }
  55         argv++;
  56
  57         /* If it is "flock FILE -c PROG", then -c isn't caught by getopt32:
  58          * we use "+" in order to support "flock -opt FILE PROG -with-opts",
  59          * we need to remove -c by hand.
  60          * TODO: in upstream, -c 'PROG ARGS' means "run sh -c 'PROG ARGS'"
  61          */
  62         if (argv[0]
  63          && argv[0][0] == '-'
  64          && (  (argv[0][1] == 'c' && !argv[0][2])
  65             || (ENABLE_LONG_OPTS && strcmp(argv[0] + 1, "-command") == 0)
  66             )
  67         ) {
  68                 argv++;
  69         }
  70
  71         if (OPT_s == LOCK_SH && OPT_x == LOCK_EX && OPT_n == LOCK_NB && OPT_u == LOCK_UN) {
  72                 /* With suitably matched constants, mode setting is much simpler */
  73                 mode = opt & (LOCK_SH + LOCK_EX + LOCK_NB + LOCK_UN);
  74                 if (!(mode & ~LOCK_NB))
  75                         mode |= LOCK_EX;
  76         } else {
  77                 if (opt & OPT_u)
  78                         mode = LOCK_UN;
  79                 else if (opt & OPT_s)
  80                         mode = LOCK_SH;
  81                 else
  82                         mode = LOCK_EX;
  83                 if (opt & OPT_n)
  84                         mode |= LOCK_NB;
  85         }
  86
  87         if (flock(fd, mode) != 0) {
  88                 if (errno == EWOULDBLOCK)
  89                         return EXIT_FAILURE;
  90                 bb_perror_nomsg_and_die();
  91         }
  92
  93         if (argv[0])
  94                 return spawn_and_wait(argv);
  95
  96         return EXIT_SUCCESS;
  97 }