CS/CE 218 Lab 5					26 September 1991

There's no report due for this lab!  The exercises contained in this
lab are intended to help you with the homework that's due tommorrow,
as well as exploring shell scripts, redirection in pipelines, tee,
join, and sed.

0. Put the directory $PUB/lab-data/lab5 in your shell's PATH
	set PATH=:$PUB/lab-data/lab5$PATH
	export PATH

1. The file $PUB/lab-data/lab5/pipe-test contains the following:

#!/bin/sh
echo "some text" | pg < $PUB/homework/hw2.txt


  (you might want to verify this...)
  Run the command
	pipe-test

  a. What happened to the output of the echo command (the words "some text")?


2. The file $PUB/lab-data/lab5/cut-tee-test contains the following:

#!/bin/sh
ps -fl | tee ps-out | cut -c79-,4-36 | tee cut-out


   Run the command
	cut-tee-test
   a. Examine the contents of ps-out and cut-out.
      Why is the content of ps-out different from the content of cut-out?
	(this should be obvious)

   b. Why do the contents of cut-out match what you saw on standard output?
	(this also should be obvious)

3. The file $PUB/lab-data/lab5/join-test contains the following:

#!/bin/sh
HW2=$PUB/hw2
if test $# -ne 3
then
	echo "need 3 arguments" >&2
	exit 1
fi
join $HW2/$1 $HW2/$2 | tee join12 | join - $HW2/$3


   a. What is the output of the following?
	join-test people live occupation

   b. What did first part of the pipeline produce?


4. This problem concerns using sed for substitutions.
   The command
	sed -e 's/xxx/yyy/'
   substitutes yyy for the first occurrence of xxx on each line in
   the command's standard input.  The command
	sed -e 's/xxx/yyy/g'
   changes EVERY occurrence of xxx to yyy on each line its standard input.
   (Think of ``g'' as ``global'')

   a. What is the exact format of the file $PUB/hw2/people?
	Are the fields separated by blanks or tabs?
	(Try editing the file and moving around in between the fields)
	What columns do the fields start in?  (In emacs, try C-x =)

   b. The file $PUB/lab-data/lab5/simple-sed-test contains the following:

#!/bin/sh
# below /  */ has two blanks, and then /	/ has a tab.
sed -e 's/  */	/g' < $PUB/hw2/people

      Run the command
	simple-sed-test
      What is the output?

   c. How could you do what was done in part (b) without using sed?

5. The file $PUB/lab-data/lab5/saving-sed contains the following:

#!/bin/sh
sed -e 's/^\([^ ]*\)  *\(.*\)$/x\2y\1z/' < $PUB/hw2/occupation

   a. Run the command
	saving-sed
      Explain the output in terms of the above command.


That's it, you're all done.
But if you want to experiment more, you can try some or all of the 
problems in /home/cs218/public/homework/lab5-extra-credit.txt
(However, you should perhaps do homework 2 first.)