homework/charfreq.c

   1 /*
   2  * Compile with:
   3  * gcc charfreq.c -o charfreq -Wall -W -Wextra -ansi -pedantic
   4  */
   5
   6 #include <ctype.h>
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9
  10 int main(int argc, char *argv[])
  11 {
  12     /*
  13      * When we partially initialize an array,
  14      * C automatically initializes the rest of it
  15      * to 0, NULL, etc, depending on the element type
  16      * of the array.
  17      * That said, the following is adequate:
  18      */
  19     unsigned int freq[26] = { 0 };    /* Frequencies for 'A' to 'Z' */
  20     unsigned int i, j, len, maxf;
  21     int c;
  22     FILE *fp;
  23
  24     /* Check argument count */
  25     if (argc != 2) {
  26         fprintf(stderr, "Usage: %s path\n", argv[0]);
  27         exit(EXIT_FAILURE);
  28     }
  29
  30     /* Open file for reading */
  31     if ((fp = fopen(argv[1], "r")) == NULL) {
  32         perror("fopen");
  33         exit(EXIT_FAILURE);
  34     }
  35
  36     /* Count frequencies */
  37     while ((c = fgetc(fp)) != EOF) {
  38         c = toupper(c);
  39         if (c >= 'A' && c <= 'Z')
  40             freq[c - 'A']++;
  41     }
  42
  43     /* Calculate size of array */
  44     len = sizeof freq / sizeof *freq;
  45
  46     /* Get max frequency */
  47     maxf = freq[0];
  48     for (i = 1; i < len; i++)
  49         if (freq[i] > maxf)
  50             maxf = i;
  51
  52     /* Print frequencies */
  53     i = maxf;
  54     for (i = freq[maxf]; i > 0; i--) {
  55         printf("%3u| ", i);
  56         for (j = 0; j < len; j++)
  57             if (freq[j] >= i)
  58                 printf("*");
  59             else
  60                 printf(" ");
  61         printf("\n");
  62     }
  63
  64     /* Print letters */
  65     printf("     ");
  66     for (i = 0; i < len; i++)
  67         printf("%c", (char)('A' + i));
  68     printf("\n");
  69
  70
  71     /*
  72      * Close file
  73      * (since we opened the file only for read,
  74      * we assume that it is safe to not check against
  75      * the return value of fclose())
  76     */
  77     (void)fclose(fp);
  78
  79     return EXIT_SUCCESS;
  80 }