How to detect empty string from fgets

c input fgets
KWJ2104 picture KWJ2104 · Nov 9, 2011 · Viewed 19.7k times · Source

I'm trying to detect the input of fgets from stdin as empty (when I press enter without entering in anything). Here is my program:

int main()
{
    char input[1000];
    printf("Enter :");
    fgets(input, 1000, stdin);
    input[strlen(input) - 1] = '\0';

    if(input != '\0'){
        printf("hi");
    }

    return 0;

}

I want to do some sort of condition which makes it not print anything, but clearly this way isn't right. I also tried NULL, which did not work.

Thanks!

Answer

orlp picture orlp · Nov 9, 2011

I think this is the most readable (but not performant):

if (strlen(input) != 0) {
    printf("hi");
}

But for the sake of teaching here is your style, but then fixed:

if (input[0] != '\0') {
    printf("hi");
}

Why input[0]? Because input acts like a pointer to the first element of the array if you compare it like that and you first have to dereference it to make the comparison useful.

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