fadvise.c

   1 #include "compat-util.h"
   2
   3 static struct fa_advice {
   4         const char *name;
   5         const int nr;
   6 } advice_table[] = {
   7         { "normal", POSIX_FADV_NORMAL },
   8         { "sequential", POSIX_FADV_SEQUENTIAL },
   9         { "random", POSIX_FADV_RANDOM },
  10         { "noreuse", POSIX_FADV_NOREUSE },
  11         { "willneed", POSIX_FADV_WILLNEED },
  12         { "dontneed" , POSIX_FADV_DONTNEED }
  13 };
  14
  15 static int usage(const char * argv0)
  16 {
  17         int i;
  18
  19         fprintf(stderr,
  20                 "Usage: %s [-a ADVICE] [-o OFFSET] "
  21                 "[-l LENGTH] FILE...\n", argv0);
  22         fprintf(stderr, "\nPossible values for advice:\n");
  23         for (i = 0; i < ARRAY_SIZE(advice_table); ++i)
  24                 fprintf(stderr, "\t%s\n", advice_table[i].name);
  25
  26         return 1;
  27 }
  28
  29 static void apply_fadvise(const char *path, off_t offset, off_t len, int advice)
  30 {
  31         int fd;
  32
  33         if ((fd = open(path, O_RDONLY|O_NOATIME)) < 0) {
  34                 fprintf(stderr, "%s: open(): %s\n", path, strerror(errno));
  35                 return;
  36         }
  37
  38         if (len <= 0) {
  39                 /* for compatibility with kernels < 2.6.6 */
  40                 struct stat sb;
  41
  42                 if (fstat(fd, &sb) < 0) {
  43                         fprintf(stderr, "%s: fstat(%d): %s\n",
  44                                 path, fd, strerror(errno));
  45                         goto out;
  46                 }
  47                 len = sb.st_size;
  48         }
  49
  50         if (posix_fadvise(fd, offset, len, advice) < 0)
  51                 fprintf(stderr,
  52                         "%s: posix_fadvise("
  53                         "offset=%lu,len=%lu,advice=%d): %s\n",
  54                         path,
  55                         (unsigned long)offset,
  56                         (unsigned long)len,
  57                         advice, strerror(errno));
  58
  59 out:
  60         close(fd);
  61 }
  62
  63 int main(int argc, char * const argv[])
  64 {
  65         off_t offset = 0;
  66         off_t len = 0;
  67         int advice = POSIX_FADV_NORMAL;
  68         int opt;
  69         int argi = 1;
  70
  71         while ((opt = getopt(argc, argv, "o:l:a:h")) != -1) {
  72                 int i;
  73                 char *err;
  74
  75                 argi += 2;
  76                 switch(opt) {
  77                 case 'o':
  78                         offset = cstr_to_off_t(optarg, &err, 10);
  79                         if (*err || offset < 0) {
  80                                 fprintf(stderr, "offset must be >= 0\n");
  81                                 return 1;
  82                         }
  83                         break;
  84                 case 'l':
  85                         len = cstr_to_off_t(optarg, &err, 10);
  86                         if (*err || len < 0) {
  87                                 fprintf(stderr, "length must be >= 0\n");
  88                                 return 1;
  89                         }
  90                         break;
  91                 case 'a':
  92                         for (i = 0; i < ARRAY_SIZE(advice_table); ++i) {
  93                                 if (strcmp(advice_table[i].name, optarg))
  94                                         continue;
  95                                 advice = advice_table[i].nr;
  96                                 break;
  97                         }
  98                         if (i < ARRAY_SIZE(advice_table))
  99                                 break;
 100                         fprintf(stderr, "advice '%s' not understood\n", optarg);
 101                         /* fall-through */
 102                 default:
 103                         return usage(argv[0]);
 104                 }
 105         }
 106
 107         if (argi >= argc)
 108                 return usage(argv[0]);
 109
 110         for (; argi < argc; ++argi)
 111                 apply_fadvise(argv[argi], offset, len, advice);
 112         return 0;
 113 }