strstr

//String find substring (till NULL)
char *mf_strstr(char *str, char *substr)
{
    char *start1 = str;
    char *pos1 = str;
    char *pos2 = substr;
    while (*pos1 != 0)
    {
        while (*pos2 != 0)
        {
            if ((*pos1++ == *pos2++) && (*pos2 == 0))
            {
                return pos1 - start1;
            }
        }
    }
    return 0;
}