Counting Character usage in text file? C

Question

Hi,
I need to count the usage of alphabetical characters in some plain text file. This is what i have came with. Basically just run through the text file and compare each character with the ASCII value of specific searched character.
When I run it, all I can see is just the first printf() string and just error of terminated status when I close the console.
I do have a text.txt file in same folder as the .exe file but I can't see anything.

Not sure if just my syntax is bad or even semantics.
Thx for help! :-)

#include <stdio.h>
#include <stdlib.h>
#define ASCIIstart 65 
#define ASCIIend 90

void main(){
    FILE *fopen(), *fp;
    int c;
    unsigned int sum;

    fp = fopen("text.txt","r");

    printf("Characters found in text: \n");

    for (int i = ASCIIstart; i <= ASCIIend; i++){
        sum = 0;
        c = toupper(getc(fp));
        while (c != EOF){
            if (c == i){
                sum = sum++;
            }
            c = toupper(getc(fp));
        }
        if (sum > 0){
            printf("%c: %u\n",i,sum);
        }
    }
    fclose(fp);
}

Answer 1

Instead of looking up the entire file for each character, you could do

FILE *fp;
int c, sum[ASCIIend - ASCIIstart + 1]={0};
fp = fopen("file.txt,"r");
if(fp==NULL)
{
    perror("Error");
    return 1;
}

int i;
while( (c = toupper(getc(fp)))!= EOF)
{
    if(c>=ASCIIstart && c<=ASCIIend)
    {
        sum[c-ASCIIstart]++;
    }
}
for(i=ASCIIstart; i<=ASCIIend; ++i)
{
    printf("\n%c: %d", i, sum[i-ASCIIstart]);
}

You must check the return value of fopen() to ensure that the file was successfully opened.

There's an array sum which holds the the number of occurrences of each character within the range denoted with ASCIIend and ASCIIstart macros.

The size of the array is just the number of characters whose number of occurrences is to be counted.

sum[c-ASCIIstart] is used because the difference between the ASCII value (if the encoding is indeed ASCII) of c and ASCIIstart would give the index associated with c.

I don't know what you meant with FILE *fopen(), fp; but fopen() is the name of a function in C used to open files.

And by

FILE *fopen(), *fp;

you gave a prototype of a function fopen().

But in stdio.h, there's already a prototype for fopen() like

FILE *fopen(const char *path, const char *mode);

yet no errors (if so) were shown because fopen() means that the function can have any number of arguments. Have a look here.

Had the return type of your FILE *fopen(); were not FILE * or if it were shown to other parameter types like int, you would definitely have got an error.

And, void main() is not considered good practice. Use int main() instead. Look here.

Answer 2

You can use a character array and parse the file contents with one time traversal and display the array count finally.

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

void main(){
FILE *fopen(), *fp;
int c;
fp = fopen("test.txt","r");
printf("Characters found in text: \n");
char charArr[26]= {0};
c = toupper(fgetc(fp));

while(c!=EOF) {
  charArr[c-'A']=charArr[c-'A']+1;
  c = toupper(fgetc(fp));
}
fclose(fp);
for(int i=0;i<26;i++){
   printf("\nChar: %c | Count= %d ",i+65,charArr[i]);
}
}

Hope this helps!!

Answer 3

because after first time you are end of the file. and your c = toupper(getc(fp)); returning -1 after that.

Answer 4

For counting just one character, you are reading the whole file and repeating this for each and every character. Instead, you can do:

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

#define ASCIIstart 65 
#define ASCIIend 90

int main(){
    FILE  *fp;
    int c, i;
    int alphabets[26] = {0};

    fp = fopen("text.txt","r");
    if (fp == NULL){
        fprintf (stderr, "Failed to open file\n");
        return -1;
    }

    while ((c = toupper(fgetc(fp))) != EOF){
        if (c >= ASCIIstart && c <= ASCIIend)
            alphabets[c - ASCIIstart]++;
    }

    fclose(fp);
    fprintf(stdout, "Characters found in text: \n");
    for (i = 0; i < 26; i++)
        fprintf (stdout, "%c: %d\n", i+ASCIIstart, alphabets[i]);
    return 0;
}

Answer 5

TLDR

Working with your code, your loops are inside-out.

I'll answer in pseudo-code to keep the concepts straightforward.

Right now you are doing this:

 FOR LETTER = 'A' TO 'Z': 
      WHILE FILE HAS CHARACTERS
           GET NEXT CHARACTER
           IF CHARACTER == LETTER 
                ADD TO COUNT FOR CHAR
           END IF
      END WHILE
 END FOR

The problem is you are running through the file with character 'A' and then reaching the end of file so nothing gets done for 'B'...'Z'

If you swapped this:

 WHILE FILE HAS CHARACTERS
      GET NEXT CHARACTER 
          FOR LETTER = 'A' TO 'Z'
              IF LETTER = UCASE(CHARACTER)
                   ADD TO COUNT FOR LETTER
              END IF
          END FOR
 END WHILE

Obviously doing 26 checks for each letter is too much so perhaps a better approach.

 LET COUNTS = ARRAY(26) 

 WHILE FILE HAS CHARACTERS
         CHARACTER := UCASE(CHARACTER)
         IF CHARACTER >= 'A' AND CHARACTER <= 'Z'
            LET INDEX = CHARACTER - 'A'
            COUNTS[INDEX]++
         ENDIF
 END WHILE

You can translate the pseudo code to C as an exercise.

Answer 6

Rewind the pointer to the beginning of the file at the end of your for loop?

This has been posted before: Resetting pointer to the start of file

P.S. - maybe use an array for your output values : int charactercount[pow(2,sizeof(char))] so that you don't have to parse the file repeatedly?

edit: was missing pow()