I don't understand this while condtition in C

Question

The task is to reproduce the behavior of the function strcpy in C. I found this code:

char    *ft_strcpy(char *s1, char *s2)
{
    int i;

    i = 0;
    while (s2[i])
    {
        s1[i] = s2[i];
        i++;
    }
    s1[i] = s2[i];
    return (s1);
}

I don't understand the while condition. Why can I just put "s2[1]" as condition? What does the condtion say in this context?

Answer 1

It checks the value of s2[i]. The string terminator '' has value 0. So it will loop until the end of the string.

The line s1[i] = s2[i]; is added to put the '' at the end.

By definition, a C-style string is a sequence of chars ended in ''. If you forget to put it at the end you probably will get into trouble.