CTS 1106 (Intro to Unix/Linux) Homework Assignment #5

Answer the following questions as briefly (but completely) as possible.  Unless otherwise stated, assume a POSIX shell (such as bash) is used.

1. Using shell wild cards, write a pattern to match any filenames where the first character is alphabetic and the last is not numeric.
2. How would you remove a file beginning with a hyphen in the $HOME/foo directory?
3. What actually happens when you use the command “cat foo > foo”?  What about “sort -o foo < foo”?  (Don't simply show the output of running those commands.)
4. What is a filter command?  From where does a filter command get its input?
5. What are the effects of using double quotes on command line arguments?
6. What are the names of two environment variables set by reading /etc/passwd when you login?  (Actually there are at least four; limit yourself to the ones listed in the syllabus.)
7. How would you add the current directory (no matter what it is) to your existing PATH?  Why would that be a bad idea?
8. If you run “PS1='\!$ '” (without the curly quotes), what sort of prompt will you get using the Bash shell?  (In POSIX compliant mode of shell, use “PS1='!$ '” instead.)  What does the prompt message mean?
9. Write a Korn or Bash shell alias to list only the hidden files of the current directory.  (Extra credit if your alias doesn't list . or .. entries.)
10. You have just used the command “tar -cvf /dev/fd0 *.sh”.  How can you repeat the command to use *.pl files instead of *.sh files, with the Bash shell, without retyping the entire command?

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