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Problems and Answers for Test 3 - Unix
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-IAN! idallen@ncf.ca

Preamble
--------

You will need to be running Floppix with networking to do
this test.  You must have network access to use telnet and
ftp to reach the machines mentioned in this test.

The test_three directory used in some of the scripts, below,
is a sub-directory of your HOME directory on the Test
Machine.  This directory will be created by your instructor
before you start your test.

Your directory test_three is where you must put your scripts
and your script output if you want the instructor to mark
them.  Your scripts do not have to create this directory;
you may assume it exists any time a script specification
requires you to use it.

Only scripts and output found under directory test_three on
the Test Machine will be marked.  Only correctly-spelled
script and file names will be marked.

Your scripts must start with a valid Script Header, as given
in class and in the Week 7 notes.

You do not have to detect or handle errors in the scripts
you write on this test.  Error handling will be covered in
Chapter 11.  For example, your script does not need to check
to see if a file or directory already exists before it tries
to make one.

Many of the scripts you write during this test will not run
without errors if you run them twice; because, the scripts
will have created files and/or directories and a second
attempt to re-create the same files and/or directories may
generate error messages.  Make sure you clean out the
results of one script run before you test your script a sec­
ond time.

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Problem A - Marks: 12
---------------------
On the Test Machine: Write an executable shell script named
several_things.sh that will do the following actions (in
this order):
  1. Display the current date.
  2. Put the pathname of the file containing your Unix mail
     into a file named current_mail.txt in the current
     directory.  (Use an existing keyword variable for the
     mail file pathname.)
  3. Put the last three lines of the Unix password file into
     a file named one_out.txt in the home directory of the
     person running the script (not in the current direc­
     tory).  (Use an existing keyword variable for the
     directory name.)
  4. Have the script set the permissions on the one_out.txt
     output file to be (a) read only for owner, (b) write
     only for group, (c) nothing for others.

#!/bin/sh -u
#  $0  (no arguments)
# This script does several small miscellaneous things.
# -IAN! idallen@ncf.ca

export PATH=/bin:/usr/bin
umask 022

date

echo "$MAIL" >current_mail.txt

tail -3 /etc/passwd >"$HOME/one_out.txt"

chmod o=r,g=w,o= "$HOME"/one_out.txt

--------------------
Problem B - Marks: 8
--------------------
On the Test Machine: Write an executable shell script named
user_finger.sh that will do the following actions (in this
order):
  1. Display the current date.
  2. Display the users on the current machine with their
     login times.
  3. Run finger to the Linux Test Machine (use the IP
     address) to show all logins, and delete from the dis­
     play the logins that are by the user running the
     script.  The output must not contain lines for the user
     name running the script.  (Hint: man whoami)

#!/bin/sh -u
#  $0  (no arguments)
# This script fingers the test machine and shows users who are not me.
# -IAN! idallen@ncf.ca

export PATH=/bin:/usr/bin
umask 022

date

who

finger @205.211.32.171 | grep -v "$(whoami)"

---------------------
Problem C - Marks: 11
---------------------
On the Test Machine: Write an executable shell script named
input_counter.sh that will do the following actions (in this
order):
  1. Display the current date.
  2. Prompt to read a line of input from the script user.
  3. Read a line of input.
  4. Output this sentence (with this exact punctuation):
        You entered: "XXX"
     where XXX is the input line entered.
  5. Output this sentence:
        Your line contains    YYY characters.
     where YYY is the count of the number of characters in
     the line of input.

#!/bin/sh -u
#  $0   (no arguments)
# This script reads a line of input and counts the characters in it.
# -IAN! idallen@ncf.ca

export PATH=/bin:/usr/bin
umask 022

date

echo 1>&2 "Enter a line of input:"

read input

echo "You entered: \"$input\""

echo "Your line contains $(echo "$input" | wc -c) characters."

---------------------
Problem D - Marks: 14
---------------------
On the Test Machine: Write an executable shell script named
who_selector.sh that will do the following actions (in this
order):
  1. Display the current date.
  2. Output this sentence (with this exact punctuation):
        Your pattern was "XXX".
     where XXX is the text string that is the first argument
     to the script.
  3. Output this sentence (with this exact punctuation):
        The file name was "YYY".
     where YYY is the text string that is the second argu­
     ment to the script.
  4. Run the who command and select only lines that contain
     the pattern that is the first argument to the script.
     Put the resulting output into the file name that is the
     second argument to the script.
  5. Output this sentence (with this exact punctuation):
        The pattern matches    ZZZ lines.
     where ZZZ is the count of the number of lines in the
     file you created.

#!/bin/sh -u
#  $0 pattern filename
# This script looks for a pattern in who output and puts output in filename.
# -IAN! idallen@ncf.ca

export PATH=/bin:/usr/bin
umask 022

date

echo "Your pattern was \"$1\"."

echo "The file name was \"$2\"."

who | grep "$1" >"$2"

echo "The pattern matches $(wc -l <"$2") lines."