In the present code of firetower, if a null string is entered in the -d or --directory command, then it defaults it to the current directory. Modify the code so that if in case a null string is passed in these arguments as directory, then it calls usage and in case of an invalid directory an error message saying "not a directory" is displayed along with call to usage.
In the present code of firetower, if a null string is entered in the -d or --directory command, then it defaults it to the current directory. Modify the code so that if in case a null string is passed in these arguments as directory, then it calls usage and in case of an invalid directory an error message saying "not a directory" is displayed along with call to usage.