comparing string gone wrong - c

Question

I got the output as unequal can you please explain me why
#include <stdio.h>
int main()
{
char str1[] = "hello";
char str2[] = "hello";
if (str1 == str2)
printf("equal");
else
printf("unequal");
return 0;
}

Answer 1

That's because == is comparing the addresses of str1 and str2 and not the
contents of the string. You have to use strcmp for this:
#include <stdio.h>
#include <string.h>
int main()
{
char str1[]="hello";
char str2[]="hello";
if(strcmp(str1, str2) == 0)
puts("equal");
else
puts("unequal");
return 0;
}
would be the correct version. See https://ideone.com/wJpL2I
Note that in C a string is just a sequence of characters that end with the
'\0'-terminating byte. str1 and str2 are both arrays, but when you do
str1 == str2 they decay into pointers and what you are comparing is the memory
location of where the arrays are stored in memory. They are two different arrays
(although they have the same content), so they memory address will be of course different, that's why you get unequal. That's why you need the
strcmp function in order to compare the contents of the char arrays.

Answer 2

You are comparing the data container’s address which are str1 and str2, if you know java then there is that equals method and contentEquals method, if you use equals method it compares the object references, but if you do contentEquals it compares the content(data) resides in the objects.
In c as you should have already known that that the name of the string has the base address in it. That’s the reason you don’t need to put &(address of operator) while using the scanf this is the soul reason when you do the str1==str2 it compares the address not the data inside the string.
In c str1 and str2 are simply 2 character array which has the \0 at the end. Now when you do
if(str1==str2) //it compares the address of
//variables not the content as
//you are comparing the base address
//of the strings str1 and str2.
The right version should be:
#include <stdio.h>
#include <string.h>
int main()
{
char str1[]="hello";
char str2[]="hello";
if(strcmp(str1, str2) == 0)
puts("equal");
else
puts("unequal");
return 0;
}
If you want to verify that you can use this, printf(“%d”, &str1); printf(“%d”, &str2); they both will not be equal.

Answer 3

When you want to compare two strings, you actually want to see if each character in one string is in the corresponding position of the other string.
The strings variables used here (str1 and str 2) are just pointers to the base addresses of those strings.
Hence, str1 == str2 means you are just comparing if both strings have the same base addresses, which, of course, is incorrect.
Here, you can make use of the string.h file which has the strcmp() or string compare function.
It works like this:
It iterates through the string, and checks the difference in the ascii values of individual characters in corresponding positions(same index value). If all characters are the same, it will return 0.
Otherwise, a positive or negative value is encountered based on the order of passing the strings to strcmp.
But in this case, it is of little importance if you get a positive or a negative value.
usage:
if (!strcmp(str1, str2))
puts("equal");
else
puts("unequal");