Replace each string of one or more blanks with a single blank

This was already asked, but I made my own program and I don't know why it doesn't work.

int c;
char blank;


while ((c = getchar()) != EOF) {
    if (c == ' ') {
        putchar(c);
        while ((c = getchar()) == ' ') {
            putchar('');
        }
    }
    putchar(c);
}

Basically, replace space with nothing is what I did. But it doesn't work. If I put '1' instead of '' it replaces spaces with 1s so I don't know what's the problem

The specific error in your code is in the way you have used the putchar() function. When using putchar() you must put a character inside, such as putchar('a'), but you cannot leave it empty. This is why you are receiving the error:

error: empty character constant

Basically, putchar() must put a character and whatever is in between the single quotes: '', is not a character.

To fix your code: you should remove the putchar('') line entirely, so your code would looks like this:

while ((c = getchar()) != EOF) {
    if (c == ' ') {
        putchar(c);
        while ((c = getchar()) == ' ') {

        }
    }
    putchar(c);
}