getchar Query

Hi All,

am new to C programming. I am following this online tutorial,

http://publications.gbdirect.co.uk/c..._programs.html

and tried this example,

Code:

---

#include <stdio>
#include <stdlib.h>
main(){
        int ch;

        ch = getchar();
        while(ch != 'a'){
                if(ch != '\n')
                        printf("ch was %c, value %d\n", ch, ch);
                ch = getchar();
        }
        exit(EXIT_SUCCESS);
}

---

and got this output,

:~/scripts$ ./char
k
char is k, value 107
char is k, value 107

I do not understand why it prints the result twice, and what is the reason for the 2nd ch = getchar() after the printf statement. Could anyone comment on this example code? Cheers.

coolboarerguy

You need to include <stdio.h>, not <stdio>, and you need an "int" in front of main.

The second getchar just keeps getting the next character from the input stream. (Since it's inside a loop, it may happen a bunch of times.)

The only way to get two statements like that is to type k twice. Even if a control character other than \n got in there, like \r or something, it would still print that instead of k.

Hi All,

sorry, that was copy/pasted from the site, whilst my code had <stdio.h> in it, as I did it from my own memory of the example code. I did pick up on the need for int instead of char. I still don't understand why it prints it twice. Cheers.

coolboarderguy

Code:

---

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

int main(void)
{
        int ch;
        ch = getchar();
        while(ch != 'a'){
                if(ch != '\n')
                        printf("char is %c, value %d\n", ch, ch);
                        getchar();
                        }
exit(EXIT_SUCCESS);
}

---

Because you lost the "ch =" in front of the getchar(); the second time.

DOH!!! Thanx.

coolboarderguy