How to determines whether two strings are equal in C language

Use strcmp function to check whether strings are equal

/*
Example: Check if strings are equals in C language
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stdbool.h>
#include <errno.h>
#include <unistd.h>

int main () {

    char str1[] = "hello!";
    char str2[] = "hello!";
    char str3[] = "halle";

    if (strcmp(str1, str2) == 0)
        printf("str1 = str2\n");

    if (strcmp(str1, str3) != 0)
        printf("str1 != str3\n");

	// Using == does not tell if strings are equal:	
    if (str1 == str2)
        printf("str1 = str2\n");

    return 0;
}