Changing gets() to txt file input

Question

I need to covert this code from a user input using gets() to scanning in an input txt file. It would also be helpful to find a way to count the number of letters in every word. Starting with 1 letter words and on.

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>


int main(void) {

    int acount, bcount, ccount, dcount, ecount, fcount, gcount, hcount, icount, jcount, kcount, lcount, mcount, ncount, ocount, pcount, qcount, rcount, scount, tcount, ucount, vcount, wcount, xcount, ycount, zcount = 0;
    char *str;

    printf("Enter any string : ");
    gets(str);

    while (*str != '\0')
    {
        if(isalpha(*str))
           {
               toupper(*str);
               switch(*str)
               {
                       case 'A':
                       ++acount;
                       break;

                       case 'B':
                       ++bcount;
                       break;

                       case 'C':
                       ++ccount;
                       break;

                       case 'D':
                       ++dcount;
                       break;

                       case 'E':
                       ++ecount;
                       break;

                       case 'F':
                       ++fcount;
                       break;

                       case 'G':
                       ++gcount;
                       break;

                       case 'H':
                       ++hcount;
                       break;

                       case 'I':
                       ++icount;
                       break;

                       case 'J':
                       ++jcount;
                       break;

                       case 'K':
                       ++kcount;
                       break;

                       case 'L':
                       ++lcount;
                       break;

                       case 'M':
                       ++mcount;
                       break;

                       case 'N':
                       ++ncount;
                       break;

                       case 'O':
                       ++ocount;
                       break;

                       case 'P':
                       ++pcount;
                       break;

                       case 'Q':
                       ++qcount;
                       break;

                       case 'R':
                       ++rcount;
                       break;

                       case 'S':
                       ++scount;
                       break;

                       case 'T':
                       ++tcount;
                       break;

                       case 'U':
                       ++ucount;
                       break;

                       case 'V':
                       ++vcount;
                       break;

                       case 'W':
                       ++wcount;
                       break;

                       case 'X':
                       ++xcount;
                       break;

                       case 'Y':
                       ++ycount;
                       break;

                       case 'Z':
                       ++zcount;
                       break;

               }//Close case
           }//Close if
    }//Close while

    printf("Number of A's: %d", acount);

}

Answer 1

Many errors in your code

1. You don't initialize all the (x)count variables to 0, read about the coma operator.

2. You used gets() which is a mean and deprecated function.

3. You passed an uninitialized pointer to gets() which is undefined behavior.

4. toupper(*str) does not modify *str.

Try this one

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

int main(void) 
{
    /* You need an array of int's with size equal to the number of letters
     * int the alphabet
     */
    int count['Z' - 'A' + 1];
    /* You need some space to store the text, `str' will become a poitner
     * when you pass it to `fgets()' pointing to an array of 1000 `chars'
     */
    char str[1000];
    /* Initialize all the counters to 0 */
    for (int i = 0 ; i < sizeof(count) / sizeof(*count) ; ++i)
        count[i] = 0;
    printf("Enter any string : ");
    /* Read the string, use `fgets()` and prevent a buffer overflow */
    if (fgets(str, sizeof(str), stdin) == NULL)
        return -1;
    /* Now count the letters */
    for (int i = 0 ; ((str[i] != '\0') && (str[i] != '\n')) ; ++i)
    {
        /* If it's not a letter, go to the next one */
        if (isalpha((int) str[i]) == 0)
            continue;
        /* It's a letter, count it at the correct position */
        count[toupper((int) str[i]) - 'A'] += 1;
    }

    /* Print the count of each letter, skipping those that did not appear */
    for (int i = 0 ; i < sizeof(count) / sizeof(*count) ; ++i)
    {
        if (count[i] == 0)
            continue;
        fprintf(stderr, "Number of %c's : %d\n", i + 'A', count[i]);
    }
    return 0;
}

Answer 2

All remarks in iharob response are correct. Read my comment on his response for extra problems. Here is a simple solution:

#include <stdio.h>

int main(void) {
    int counts[256] = { 0 };
    int c;

    printf("Enter any string: ");
    while ((c = getchar()) != EOF && c != '\n') {
        counts[c & 255]++;
    }
    printf("Number of A's: %d", counts['a'] + counts['A']);
    return 0;
}

EDIT: here is a solution to handle a file instead of a line of input:

#include <stdio.h>

int main(int argc, char **argv) {
    long long int counts[256] = { 0 };
    int c;
    FILE *f;

    if (argc < 2) {
        fprintf(stderr, "usage: %s FILE\n", argv[0]);
        exit(2);
    }
    if ((f = fopen(argv[1], "r")) == NULL) {
        fprintf(stderr, "%s: cannot open %s\n", argv[0], argv[1]);
        exit(1);
    }
    while ((c = getc(f)) != EOF) {
        counts[c & 255]++;
    }
    fclose(f);
    printf("Number of A's: %lld", counts['a'] + counts['A']);
    return 0;
}