Problem
1. Write a program that accepts a directory name as argument, changes to that directory, and displays its absolute pathname. Is the change permanent?
2. Write a program that lists from the current directory all ordinary filenames whose size exceeds 100,000 bytes. It should also remove all zero-sized files.
3. Write a program that sets the user mask to zero before creating a file foo. Now, change the permissions of foo to
(i) 764,
(ii) 440. The previous value of the mask should be restored before program termination.