How do I properly compare strings in C?

Question

I am trying to get a program to let a user enter a word or character, store it, and then print it until the user types it again, exiting the program. My code looks like this:

#include <stdio.h>

int main()
{
    char input[40];
    char check[40];
    int i=0;
    printf("Hello!
Please enter a word or character:
");
    gets(input);   /* obsolete function: do not use!! */
    printf("I will now repeat this until you type it back to me.
");

    while (check != input)
    {
        printf("%s
", input);
        gets(check);   /* obsolete function: do not use!! */
    }

    printf("Good bye!");
    

    return 0;
}

The problem is that I keep getting the printing of the input string, even when the input by the user (check) matches the original (input). Am I comparing the two incorrectly?

Answer 1

You can't (usefully) compare strings using != or ==, you need to use strcmp:

while (strcmp(check,input) != 0)

The reason for this is because != and == will only compare the base addresses of those strings. Not the contents of the strings themselves.