Solutions to HW 1
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1. touch ./-u

2. There are many solutions, e.g.,
    a) ls *.???
    b) ls [GPR]*
    c) ls [MJC]*[nc]*
    d) ls *.*

3. In the first command, the subdirectories under 'oldaccounts' will be
copied over, so that the new copies will have 'newaccounts' as their
parent directory. In the second command, 'oldaccounts' (and all its
descendants) itself will be copied over, so that the new copies will continue
to have 'oldaccounts' as their parent directory.

4. who | cut -d" " -f1

5. Do a 'man cal' to get the story!