miscutils/readahead.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * readahead implementation for busybox
   4  *
   5  * Preloads the given files in RAM, to reduce access time.
   6  * Does this by calling the readahead(2) system call.
   7  *
   8  * Copyright (C) 2006  Michael Opdenacker <michael@free-electrons.com>
   9  *
  10  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  11  */
  12
  13 //usage:#define readahead_trivial_usage
  14 //usage:       "[FILE]..."
  15 //usage:#define readahead_full_usage "\n\n"
  16 //usage:       "Preload FILEs to RAM"
  17
  18 #include "libbb.h"
  19
  20 int readahead_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  21 int readahead_main(int argc UNUSED_PARAM, char **argv)
  22 {
  23         int retval = EXIT_SUCCESS;
  24
  25         if (!argv[1]) {
  26                 bb_show_usage();
  27         }
  28
  29         while (*++argv) {
  30                 int fd = open_or_warn(*argv, O_RDONLY);
  31                 if (fd >= 0) {
  32                         off_t len;
  33                         int r;
  34
  35                         /* fdlength was reported to be unreliable - use seek */
  36                         len = xlseek(fd, 0, SEEK_END);
  37                         xlseek(fd, 0, SEEK_SET);
  38                         r = readahead(fd, 0, len);
  39                         close(fd);
  40                         if (r >= 0)
  41                                 continue;
  42                 }
  43                 retval = EXIT_FAILURE;
  44         }
  45
  46         return retval;
  47 }