homework/charfreq.c

   1 #include <ctype.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4
   5 int main(int argc, char *argv[])
   6 {
   7     /*
   8      * When we partially initialize an array,
   9      * C automatically initializes the rest of it
  10      * to 0, NULL, etc, depending on the element type
  11      * of the array.
  12      * That said, the following is adequate:
  13      */
  14     unsigned int freq[26] = { 0 };    /* Frequencies for 'A' to 'Z' */
  15     unsigned int i, j, maxf;
  16     int c;
  17     FILE *fp;
  18
  19     /* check argument count */
  20     if (argc != 2) {
  21         fprintf(stderr, "usage: %s path\n", argv[0]);
  22         exit(EXIT_FAILURE);
  23     }
  24
  25     /* open file for reading */
  26     if ((fp = fopen(argv[1], "r")) == NULL) {
  27         perror("fopen");
  28         exit(EXIT_FAILURE);
  29     }
  30
  31     /* count frequencies */
  32     while ((c = fgetc(fp)) != EOF) {
  33         c = toupper(c);
  34         if (c >= 'A' && c <= 'Z')
  35             freq[c - 'A']++;
  36     }
  37
  38     /* get max frequency */
  39     maxf = freq[0];
  40     for (i = 1; i < sizeof freq / sizeof *freq; i++)
  41         if (freq[i] > maxf)
  42             maxf = i;
  43
  44     /* print frequencies */
  45     i = maxf;
  46     for (i = freq[maxf]; i > 0; i--) {
  47         printf("%3u| ", i);
  48         for (j = 0; j < sizeof freq / sizeof *freq; j++)
  49             if (freq[j] >= i)
  50                 printf("*");
  51             else
  52                 printf(" ");
  53         printf("\n");
  54     }
  55
  56     /* print letters */
  57     printf("     ");
  58     for (i = 0; i < sizeof freq / sizeof *freq; i++)
  59         printf("%c", (char)('A' + i));
  60     printf("\n");
  61
  62
  63     /*
  64      * close file
  65      * (since we opened the file only for read,
  66      * we assume that it is safe to not check against
  67      * the return value of fclose())
  68     */
  69     (void)fclose(fp);
  70
  71     return EXIT_SUCCESS;
  72 }