Loop counter prints same value each time with different input

Question

So this loop is supposed to count the number of numerical chars in a line, but it prints the same value each time (6356732). What am I doing wrong?

if((i >= '0') && (i <= '9'))
    {
        printf("%c\n", i); 
        count = count++;        
    }

count is just declared 'int count = 0;'.

edit; I made a change suggested below but the output hasn't changed?

while(fscanf(f, "%c\n", &i) !=EOF) 
{
    if((i >= '0') && (i <= '9')) 
    {
        count = 0;
        sum = 0;
        printf("%c\n", i);
        count++;        
        sum++;
    }
}

edit 2; OK so I've got the program working as intended with the help of all you lovely folk! Thankyou very much!

 while(fscanf(f, "%c\n", &i) !=EOF) 
{
    if((i >= '0') && (i <= '9')) 
    {
        printf("%c\n", i); 
        count++;                

    }
}

count is defined at zero at the start of the program.

Can you paste the whole loop? In this snippet `i` isn't changing at all; so it's not surprising that it's printing the same value. Did you maybe mean to printf `count`? — Alejandro C., Nov 21 '16 at 19:53
@cbes You are initializing `count` to `0` each time you find a digit. You only need to initialize it once. Besides I don't see `i` is defined. You are reading in `f` but comparing with `i`? — P.P, Nov 21 '16 at 20:02
where do you get 6356732? Nothing in yr code prints the count (which will always be zero in what you show) — pm100, Nov 21 '16 at 20:05
Yeah I've removed the count=0. However, count is still ending up with a value of '6356732'. Count is being printed outside the loop, further down in main(). Also the values of i are saved in a text file earlier in the process, this loop is reading from the file and printing the results to the console. — , Nov 21 '16 at 20:06
`count = 0` should go before the `while` loop. Is your `printf` producing the characters you expect to see? — yano, Nov 21 '16 at 20:13
@cbes I can't see how exactly you read from the file and count. I have updated my answer with an example that should help to see the problem in your code and you can modify it to suit your needs. — P.P, Nov 21 '16 at 20:14
printf seems to be working perfectly. I'll attach an image of the [output](http://i.imgur.com/GVF5YWf.png) — , Nov 21 '16 at 20:18

score 3 · Answer 1 · edited Sep 14 '17 at 03:38

count = count++;

is undefined behaviour. For your purpose, you just need:

count++;

Here's a simple example to read a line from stdin and count chars (which you can easily modify to suit your file reading and counting):

#include <stdio.h>

int main(void) 
{   
    char line[256];
    int count = 0;
    int sum = 0;
    size_t i = 0;

    if (fgets(line, sizeof line, stdin)) {
       while(line[i]) {
          if((line[i] >= '0') && (line[i] <= '9')) { 
             printf("%c\n", line[i]); 
             count++; 
             sum = sum + line[i] - '0';
          }
          i++;
       }  
    }

    printf("%d %d\n", sum, count);
    return 0;
}

score 2 · Accepted Answer · edited May 23 '17 at 11:59

2

You should just use count++; or count = count + 1;, because count = count++; is not defined. You can read more about the subject in this post.

edited May 23 '17 at 11:59

Community

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answered Nov 21 '16 at 19:54

Honza Dejdar

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Loop counter prints same value each time with different input

2 Answers2