coreutils/sync.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Mini sync implementation for busybox
   4  *
   5  * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
   6  * Copyright (C) 2015 by Ari Sundholm <ari@tuxera.com>
   7  *
   8  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   9  */
  10 //config:config SYNC
  11 //config:       bool "sync (769 bytes)"
  12 //config:       default y
  13 //config:       help
  14 //config:       sync is used to flush filesystem buffers.
  15 //config:config FEATURE_SYNC_FANCY
  16 //config:       bool "Enable -d and -f flags (requires syncfs(2) in libc)"
  17 //config:       default y
  18 //config:       depends on SYNC
  19 //config:       help
  20 //config:       sync -d FILE... executes fdatasync() on each FILE.
  21 //config:       sync -f FILE... executes syncfs() on each FILE.
  22
  23 //applet:IF_SYNC(APPLET_NOFORK(sync, sync, BB_DIR_BIN, BB_SUID_DROP, sync))
  24
  25 //kbuild:lib-$(CONFIG_SYNC) += sync.o
  26
  27 /* BB_AUDIT SUSv3 N/A -- Matches GNU behavior. */
  28
  29 //usage:#define sync_trivial_usage
  30 //usage:       ""IF_FEATURE_SYNC_FANCY("[-df] [FILE]...")
  31 //usage:#define sync_full_usage "\n\n"
  32 //usage:    IF_NOT_FEATURE_SYNC_FANCY(
  33 //usage:       "Write all buffered blocks to disk"
  34 //usage:    )
  35 //usage:    IF_FEATURE_SYNC_FANCY(
  36 //usage:       "Write all buffered blocks (in FILEs) to disk"
  37 //usage:     "\n        -d      Avoid syncing metadata"
  38 //usage:     "\n        -f      Sync filesystems underlying FILEs"
  39 //usage:    )
  40
  41 #include "libbb.h"
  42
  43 /* This is a NOFORK applet. Be very careful! */
  44
  45 int sync_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  46 int sync_main(int argc UNUSED_PARAM, char **argv IF_NOT_DESKTOP(UNUSED_PARAM))
  47 {
  48 #if !ENABLE_FEATURE_SYNC_FANCY
  49         /* coreutils-6.9 compat */
  50         bb_warn_ignoring_args(argv[1]);
  51         sync();
  52         return EXIT_SUCCESS;
  53 #else
  54         unsigned opts;
  55         int ret = EXIT_SUCCESS;
  56
  57         enum {
  58                 OPT_DATASYNC = (1 << 0),
  59                 OPT_SYNCFS   = (1 << 1),
  60         };
  61
  62         opts = getopt32(argv, "^" "df" "\0" "d--f:f--d");
  63         argv += optind;
  64
  65         /* Handle the no-argument case. */
  66         if (!argv[0])
  67                 sync();
  68
  69         while (*argv) {
  70                 int fd = open_or_warn(*argv, O_RDONLY);
  71
  72                 if (fd < 0) {
  73                         ret = EXIT_FAILURE;
  74                         goto next;
  75                 }
  76                 if (opts & OPT_DATASYNC) {
  77                         if (fdatasync(fd))
  78                                 goto err;
  79                         goto do_close;
  80                 }
  81                 if (opts & OPT_SYNCFS) {
  82                         /*
  83                          * syncfs is documented to only fail with EBADF,
  84                          * which can't happen here. So, no error checks.
  85                          */
  86                         syncfs(fd);
  87                         goto do_close;
  88                 }
  89                 if (fsync(fd)) {
  90  err:
  91                         bb_simple_perror_msg(*argv);
  92                         ret = EXIT_FAILURE;
  93                 }
  94  do_close:
  95                 close(fd);
  96  next:
  97                 ++argv;
  98         }
  99
 100         return ret;
 101 #endif
 102 }