commands/simple/fortune.c

   1 /*  fortune  -  hand out Chinese fortune cookies        Author: Bert Reuling */
   2
   3 #include <sys/types.h>
   4 #include <sys/stat.h>
   5 #include <time.h>
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <stdio.h>
   9
  10 #define COOKIEJAR "/usr/lib/fortune.dat"
  11
  12 static char *Copyright = "\0Copyright (c) 1990 Bert Reuling";
  13 static unsigned long seed;
  14
  15 _PROTOTYPE(int main, (int argc, char **argv));
  16 _PROTOTYPE(unsigned long magic, (unsigned long range));
  17
  18 int main(argc, argv)
  19 int argc;
  20 char *argv[];
  21 {
  22   int c1, c2, c3;
  23   struct stat cookie_stat;
  24   FILE *cookie;
  25
  26   if ((cookie = fopen(COOKIEJAR, "r")) == NULL) {
  27         printf("\nSome things better stay closed.\n  - %s\n", argv[0]);
  28         exit (-1);
  29   }
  30
  31   /* Create seed from : date, time, user-id and process-id. we can't get
  32    * the position of the moon, unfortunately.
  33    */
  34   seed = time( (time_t *) 0) ^ (long) getuid() ^ (long) getpid();
  35
  36   if (stat(COOKIEJAR, &cookie_stat) != 0) {
  37         printf("\nIt furthers one to see the super guru.\n  - %s\n", argv[0]);
  38         exit (-1);
  39   }
  40   fseek(cookie, magic((unsigned long) cookie_stat.st_size), 0); /* m ove bu magic... */
  41
  42   c2 = c3 = '\n';
  43   while (((c1 = getc(cookie)) != EOF) && ((c1 != '%') || (c2 != '%') || (c3 != '\n'))) {
  44         c3 = c2;
  45         c2 = c1;
  46   }
  47
  48   if (c1 == EOF) {
  49         printf("\nSomething unexpected has happened.\n  - %s", argv[0]);
  50         exit (-1);
  51   }
  52
  53   c2 = c3 = '\n';
  54   while (((c1 = getc(cookie)) != '%') || (c2 != '%') || (c3 != '\n')) {
  55         if (c1 == EOF) {
  56                 rewind(cookie);
  57                 continue;
  58         }
  59         putc(c2, stdout);
  60         c3 = c2;
  61         c2 = c1;
  62   }
  63   putc('\n', stdout);
  64   fclose(cookie);
  65   return (0);
  66 }
  67
  68 /*  magic  -  please study carefull: there is more than meets the eye */
  69 unsigned long magic(range)
  70 unsigned long range;
  71 {
  72
  73   seed = 9065531L * (seed % 9065533L) - 2 * (seed / 9065531L) + 1L;
  74   return (seed % range);
  75 }