strcmp() won't work for you because it expects an exact match.
you can call strstr() to see if the line contains "-hello". If it does, then check for anything following to see if something other than spaces. You may need to do additional checks if there is a chance that the line will contains other stuff, for example "-HelloWorld" because strstr() will return valid pointer for that also.
char* ptr = strstr(line, "-hello");
if( ptr != NULL)
// now check remainder of string to see if
// there is anything but spaces following the
// text -Hello.