IT 441: Network Services Administration

IT 441: Network Services Administration
Class #03 Exercise

Complete by: 2/11/2018

Log in to users.cs.umb.edu

Run the ssh client
Use the values in the table below to connect to users.

ssh configuration parameter	value
protocol	ssh
ssh version	2
ssh port	22
host	users.cs.umb.edu
user name	your unix username
Authentication method	password

Enter your password
A dialog box will appear on the screen into which you must type the password for your Unix account.
Make sure you are in your home directory
```
                cd
```
Go to your it441 directory
```
                cd  it441
```
Go to your ex directory
```
                cd  ex
```
Create an ex03 directory
```
                mkdir  ex03
```
Go to your ex03 directory
```
                cd  ex03
```
Execute the script command
```
                script
```
Use your perlsession alias to start the re.pl script.
```
                perlsession
```
(NOTE: If the perlsession alias is not recognized, or if re.pl cannot run, then double-check your Perl configuration, as well as your login shell vs. subshell environments!)

Just so that you understand what you are doing here, when you see an item like this...
        perl>  $int_numb = 57 ;
...that means you have the prompt perl> , at which you should type the following Perl code $int_numb = 57 ; and press Enter. The resulting session will feature the Perl prompt, the code you type, and any output that results.
Also, in terms of entering the code at the prompt, you may in fact find it easier to copy the code from your browser and paste it in at the Perl prompt. This way, you can focus your attention less on typing and more on comprehending the code:

What are the parts to the code?

Why are they here?

How do they contribute to the output/result?

If you changed the code, in one way or another, how would that affect the output/result?

Asking questions like these and experimenting are how you develop your skill at Perl programming and many other tasks!

Practice with scalar variable types

Integer numbers

perl>  $int_numb = 57 ;
perl>  print $int_numb ;

Floating point numbers

perl>  $decimal = 85.35 ;
perl>  print $decimal ;

Long integer numbers

perl>  $long_int = 10000000000000000001 ;
perl>  print $long_int ;

Strings

perl>  $team = 'Red Sox' ;
perl>  print $team ;

Practice with variable names

Meaningful variable names

perl>  $first_name = "Dustin" ;
perl>  $last_name  = "Pedroia" ;
perl>  print $first_name . " " . $last_name ;

Long variable names

perl>  $number_of_times_the_sox_have_won_world_series_this_century = 3 ;
perl>  print $number_of_times_the_sox_have_won_world_series_this_century ;

(Does this work? If not, why? If so, why shouldn't you do it?)

Illegal variable names

perl>  S1st_name = 'Koji' ;
perl>  Sclass = 'IT 441' ;

Practice with operators

Arithmetic operators

perl>  print 4 + 5 ;
perl>  print 4 - 5 ;
perl>  print 4 * 5 ;
perl>  print 20 / 5 ;
perl>  print 20 / 3 ;
perl>  print int (20 / 3) ;
perl>  print 20 % 3 ;
perl>  print 2 ** 3 ;

String operators

perl>  $team = 'Red Sox' ;
perl>  $city = "Boston" ;
perl>  print $city . " " . $team ;
perl>  print $team x 3 ;
perl>  $new_team = $team x 3 ;
perl>  print $new_team ;

Practice with statements

print statement

perl>  print "I root for the ", $city, " ", $team ;

Practice with the rules of precedence

Define some variables

perl>  $a = 3 ;
perl>  $b = 4 ;
perl>  $c = 5 ;

Addition and multiplication operators

perl>  print $a + $b * $c ;
perl>  print ($a + $b) * $c ;

Subtraction and division operators

perl>  print $a - $b ;
perl>  print $a - $b / $c ;
perl>  print $b / $c ;
perl>  print ($a - $b) / $c ;
perl>  print $c % $b - $a ;
perl>  c % b ;
perl>  print $c % ($b - $a) ;

Exponentiation

perl>  print $c - $a ** $b ;
perl>  print $a ** $b ;
perl>  print ($c - $a) ** $b ;

End the Perl Session
```
perl>  exit
```

End the script session

Use the exit command. You should then have a file called typescript in your current working directory.