"printf" printing twice despite being called only once

Asked Oct 22 '22 at 14:55

Active Oct 22 '22 at 14:55

Viewed 29 times

I'm almost ashamed to ask such a basic question but this makes no sense. Why does the question print twice ? I've tried adding a sleep to make sure it's not the enter key staying pressed too long, but it still did that. Note that it only happens on the second call onwards, which is definitely a clue.

char question() {
    char response = ' ';
    while(response != '+' && response != '-' && response != '=') {
        printf("Respond with + or - or  = : ");
        scanf("%c", &response);
    }
    return response;
}

asked Oct 22 '22 at 14:55

ice-wind

This is the infamous newline character, that is in fact a character in the input stream/ – Cheatah Oct 22 '22 at 14:57
So scanf reads the `newline` from my **previous** input !? – ice-wind Oct 22 '22 at 15:00
1

`scanf(" %c", &response);` Put a space before `%c` to skip leading whitespace. – Retired Ninja Oct 22 '22 at 15:01
1

No, `scanf` reads the input stream, the previous time it first time it read the character, the second time the newline character as in the "enter key" you pressed. – Cheatah Oct 22 '22 at 15:01

"printf" printing twice despite being called only once

0 Answers0