is that char null terminator is including in the length count

Question

#include 

int main(int argc, char *argv[]) {
   char s[]=\"help\";
   printf(\"%d\",strlen(s));  
}

Why the above output is 4, isn

Answer 1

strlen: Returns the length of the given byte string not including null terminator;

char s[]="help";
strlen(s) should return 4.

sizeof: Returns the length of the given byte string, include null terminator;

char s[]="help";
sizeof(s) should return 5.

Answer 2

strlen() does not count the number of characters in the array (in fact, this might not even be knowable (if you only have a pointer to the memory, instead of an array). It does, as you have found out, count the number of characters up to but not including the null character. Consider char s[] = {'h','i','\0','t','h','e','r','e'};

Answer 3

strlen counts the elements until it reaches the null character, in which case it will stop counting. It won't include it with the length.

Answer 4

It's 4.

strlen() counts the number of characters up to, but not including, the first char with a value of 0 - the nul terminator.

Answer 5

strlen(const char* ptr) returns the length of the string by counting the non-zero elements starting at until reaches zero. So '\0' doesn't count.

I recommend that you consult the reference like link for questions like this.

It's clearly stated as:

 A C string is as long as the number of characters between the beginning 
 of the string and the terminating null character (without including the
 terminating null character itself).