release/src/router/busybox/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 tarball for details.
  11  */
  12
  13 #include "libbb.h"
  14
  15 int readahead_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  16 int readahead_main(int argc, char **argv)
  17 {
  18         int retval = EXIT_SUCCESS;
  19
  20         if (argc == 1) bb_show_usage();
  21
  22         while (*++argv) {
  23                 int fd = open_or_warn(*argv, O_RDONLY);
  24                 if (fd >= 0) {
  25                         off_t len;
  26                         int r;
  27
  28                         /* fdlength was reported to be unreliable - use seek */
  29                         len = xlseek(fd, 0, SEEK_END);
  30                         xlseek(fd, 0, SEEK_SET);
  31                         r = readahead(fd, 0, len);
  32                         close(fd);
  33                         if (r >= 0)
  34                                 continue;
  35                 }
  36                 retval = EXIT_FAILURE;
  37         }
  38
  39         return retval;
  40 }