How do I properly compare strings in C?

c string strcmp
nmagerko picture nmagerko · Nov 4, 2011 · Viewed 459.5k times · Source

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!\nPlease enter a word or character:\n");
    gets(input);
    printf("I will now repeat this until you type it back to me.\n");

    while (check != input)
    {
        printf("%s\n", input);
        gets(check); 
    }

    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

Mysticial picture Mysticial · Nov 4, 2011

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.

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