IT 441: Network Services Administration
Class #07 Exercise

Complete by: 3/4/2018

Log in to users.cs.umb.edu

• Log in to a Windows machine
  Enter your Unix username as the account name. Then enter your password.
• 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 ex07 directory
  

  mkdir  ex07

• Go to your ex07 directory
  

  cd  ex07

• 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!)

Writing to a another terminal, instead of a file

Open a second ssh session for yourself on users.cs.umb.edu.

(No need to use script or perlsession here!)

Execute the tty command to get your terminal's path, which will be of this form: /dev/pts/23 Below, replace /dev/pts/23 with the path that the tty command gave you

perl>  open ( OUT4 , '>' , '/dev/pts/23' ) or die $!;

perl>  print OUT4 "first\n";

perl>  print OUT4 "second\n";

perl>  print OUT4 "third\n";

perl>  print OUT4 "fourth\n";

perl>  close (OUT4);

(Look at your other terminal? What happened, and why?)

Piping into your script code -- from another process

Here, we will use a Linux command to choose all the usernames that contain "ll" and read them into our script code. This is to avoid the longer output we would get from printing every username!

perl>  open ( IN5 , '-|' , 'ls /home | grep ll' ) or die $!;

perl>  while (<IN5>) { chomp ; print $_ ; print ", " ; } print "\n" ;

perl>  close (IN5);

Piping from your script code -- into another process

perl>  open ( OUT6 , '|-' , 'sort -r' ) or die $!; 

perl>  while (<STDIN>) { $_ = uc $_ ; print OUT6 $_ ; } 

At this point, it will appear to stall, but what's actually happening is this: It is waiting for you to enter lines of text. Just type something and press Enter. Then, do this again, at least four more times. When you are done entering lines of text, press Ctrl+D. This signals the end of input so that the while loop stops executing.

perl>  close (OUT6);

(What happens after you enter the line close (OUT6); ?)

Piping in both directions

perl>  open ( IN7 , '-|' , 'ls /home | grep ll' ) or die $!;

perl>  open ( OUT7 , '|-' , 'sort -r' ) or die $!; 

perl>  while (<IN7>) { $_ = uc $_ ; print OUT7 ; } 

perl>  close (IN7); 

perl>  close (OUT7);

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.