Overview

This assignment will give you an overview of the UNIX shell. The shell is your basic means of interaction with the system. Because you are using a cs9e account, we have customized your shell for use in this course. Shell accounts that you have on other systems and for other classes will more than likely look slightly different, but they all behave similarly. This assignment will teach you how to use the shell and how to customize it for your own needs.

Reading

Das: Ch. 7, 9 (excluding 9.10), 10

Part 1 - Metacharacters And Quoting

Perform the following operations, and be prepared to explain the commands you used to a tutor in addition to recording them in your transcript.

1. From within your home directory, perform a ls operation shows all directories that begin with a ".". You should not see plain files, and you should not see the contents of these directories. Example:

   ~ $ ls _____________
   ../  ./  .ssh/  .ssh2/  .sunw/  .tin/
   

2. Use quoting or escaping where necessary (and only where necessary) to properly create directories with the following names:

   1. !*
   2. $HOME
   3. ...
   4. "What's For Dinner?"
   5. -

   IE, if you do an ls, you should see:

   $ ls -a
   !*\  -  .  ..  ...  $HOME  "What's For Dinner?"
   

3. List all files in /usr/bin which begin with the letter a, b, or c.

4. Echo every 2 letter combination of a, b, c, and d including doubles. IE:

   $ echo __________
   aa ab ac ad ba bb bc bd ca cb cc cd da db dc dd
   

Part 2 - Environment Customization

Make the necessary changes to your shell configuration files to do the following. You will need to show the results as well as the changes to your tutor for checkoff. After being checked off, feel free to undo these changes.

1. Change your prompt.
2. Create a ~/.todo which is displayed whenever you login remotely but not when you open a terminal in X.
3. Add your name to your 'finger' information.

Part 3 - Piping and Redirection

The file ~${MASTERDIR}/hw/01.02-shell/al.batters.88 contains the Final Official 1988 American League batter statistics. The "position" category lists positions at which the player played 20 or more games. Each line of the file contains the following information about a player, organized into fields separated by one or more blanks:

1. his name
2. his team
3. his position or positions
4. whether he bats right-handed or left-handed
5. his batting average (hits divided by at-bats)
6. the number of games he played
7. how many "at bats" he had
8. how many runs he scored
9. how many hits he had
10. how many total bases he had (1 for each single, 2 for each double, etc.
11. how many doubles
12. how many triples
13. how many home runs
14. how many runs batted in
15. how many sacrifice hits
16. how many sacrifice flies
17. how many times he was hit by a pitch
18. how many walks
19. how many intentional walks
20. how many times he struck out
21. how many stolen bases
22. how many times he was caught stealing
23. how many double-plays he hit into
24. his on-base-average

Use piping and UNIX commands you have learned about to answer the following questions. Be prepared to explain the commands you used to a tutor in addition to recording them in your transcript.

1. Devise a single pipeline (a command constructed entirely of one or more pipes) that prints the names and batting averages of the ten players whose batting averages are the highest. (Hint: Our solution uses tr, sort, cut, and head)
2. Devise a single pipeline that prints the name of the batter who played the most games of all batters who hit no home runs along with the number of games he played. (Hint: Our solution uses tr, cut, sort, and head)
3. Devise a pair of commands, neither containting any semicolons, that prints the names of batters that were in the top ten both in batting average and in number of home runs. The first command will generate a file containing the names of the players with the top ten batting averages; the next command will compare these names with the top ten home run hitters. (Hint: Our solution uses tr, sort, cut, head, and comm. Make sure that hitters with the same number of home runs are arranged in order by batting average.)

You may assume that there is at least one AL player who hit no home runs in 1988, that at least one player ranked in the top ten both in batting average and in the number of home runs, and that at most one player with a given number of home runs also has one of the top ten batting averages.

Note the difference between sorting twice and sorting on two keys. Your pipeline will run more efficiently if head appears as early in the pipeline as possible. (Why?)

Part 1

• Student has correct answers for all questions and can intelligently explain how they reached those answers.
• Student can adequately explain how quoting works in the shell.
• Student can adequately explain how *, [], and {} wildcard matching works in the shell.

Part 2

• Student has changed their shell prompt by properly modifying their shell configuration files.
• Student's ~/.todo file is shown when they login.
• Student's finger information is set correctly.

Part 3

• Student shows script containing the required commands.
• Student can intelligently describe how piping works and demonstrate their understanding of standard input and output.