Section 15.4 contained several statements about the permissions required for various file-system operations. Use shell commands or write programs to verify or answer the following:

a) Removing all owner permissions from a file denies the file owner access, even though group and other do have access.

b) On a directory with read permission but not execute permission, the names of files in the directory can be listed, but the files themselves can't be accessed, regardless of the permissions on them.

c) What permissions are required on the parent directory and the file itself in order to create a new file, open a file for reading, open a file for writing, and delete a file? What permissions are required on the source and target directory to rename a file? If the target file of a rename operation already exists, what permissions are required on that file? How does setting the sticky permission bit (chmod +t) of a directory affect renaming and deletion operations?