Assume permissions on a file allow you to write to the file but not to delete it.

a. Give a command to empty the file without invoking an editor.
b. Explain how you might have permission to modify a file that you cannot
delete.

a. $ cat /dev/null > filename
b. To delete a file, you must have write and execute permission for the direc-
tory holding the file. To write to a file, you must have write permission

for the file and execute permission for the parent directory. When you
have write permission only for a file and execute permission only for the
directory holding the file, you can modify but not delete the file.