Counting input characters in C

Question

I have just started learning C, been reading a C textbook by Keringhan and Ritchie. There was this example in the textbook, counting characters from user input. Here's the code:

#include <stdio.h>

main() 
{
    long nc;
    nc = 0;

    while(getchar() != EOF) {
        if (getchar() != 'q')       
            ++nc;
        else 
            break;      
    }

    printf("%ld\n", nc);        
}

The problem is, when I execute the code, if I input only one character per line, when I input "q" to break, it doesn't do so. I have to type some word per line, only after that it will break the loop. Also, it only counts the half of the characters of the word. I.e. if I input

a
b
russia

it will only print '5' as final result.

Could you please explain to me why is this happening?

The above code is odd. You should store the while getchar() as a variable and then check if the variable is == 'q' instead of calling getchar() again. — David, Mar 22 '14 at 12:01
In other words, your code is ignoring every other `getchar()` call (where the comparison to 'q' and counting characters is concerned). This makes you susceptible to not seeing the `q`, and it makes your count divide the true number of key presses by 2. — mah, Mar 22 '14 at 12:10
I used a variable instead of using getchar() the second time, but now I think it counts Enter as well. Is it supposed to be like that. — kulan, Mar 22 '14 at 14:29
I'm sure that K&R doesn't contain such broken code, unless you got one of the (sometimes atrocious) translations in your hand. — vonbrand, Mar 22 '14 at 15:00
It didn't actually. I added IF statements myself, because otherwise I would know how to exit the loop. — kulan, Mar 22 '14 at 15:32

score 1 · Accepted Answer · edited May 23 '17 at 11:49

1

This works, but only when you finish off with an Enter. So, this will count the characters until the first "q" appears. That is just how getchar() and getc(stdin) work.

#include <stdio.h>

int main() {
    char c = 0;
    long count = 0;
    short int count_linebreak = 1; // or 0

    while((c = getchar()) != EOF) {
        if(c != 'q' && (count_linebreak || (!count_linebreak && c != '\n'))) {
            ++count;
        }else if(c == 'q') {
            printf("Quit\n");
            break;
        }
    }

    printf("Count: %ld\n",count);

    return 0;
}

A StackOverflow question about reading stdin before enter C read stdin buffer before it is submit

edited May 23 '17 at 11:49

Community

1
1

answered Mar 22 '14 at 12:08

David

4,313
1
21
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So when you press Enter, it will aslo be counted? Becuase it does in my code. E.g. I input 3 chars in 3 lines, and I get Count = 6. – kulan Mar 22 '14 at 14:27
Line Breaks '\n' are characters and will be counted. I will update the code to not count line breaks also. The enter statement from above means that if you type q and don't press enter, nothing will happen. – David Mar 22 '14 at 14:43
not quite got your code with count_linebreak, but when it is set to 1, same problem, it counts Enter as well. And when it is set to 0, the program terminates after the first Enter. – kulan Mar 22 '14 at 15:31
It shouldn't end after the first enter. Make sure you update the else statement so it checks if c == 'q', before it was just an else. When set to 1, it should count line breaks, when set to 0 it shouldn't. – David Mar 22 '14 at 15:38

Counting input characters in C

1 Answers1