IT 441: Network Services Administration

IT 441: Network Services Administration
Class #15 Exercise

Complete by: 4/20/2018

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 ex15 directory
```
                mkdir  ex15
```
Go to your ex15 directory
```
                cd  ex15
```
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!)

(NOTE: Parts of this exercise taken from the following page: https://perldoc.perl.org/perldsc.html)

Arrays of arrays - What will not work

perl>  @array_1 = ( "fred", "barney" ) ;

perl>  @array_2 = ( "george", "jane", "elroy" ) ;

perl>  @array_3 = ( "homer", "marge", "bart" ) ;

perl>  @array_of_arrays = ( @array_1 , @array_2 , @array_3 ) ;

perl>  print "Array of arrays length is: " . scalar (@array_of_arrays) . "\n" ;

perl>  foreach $value (@array_of_arrays) { print "$value\n" ; }

Arrays of arrays - What will work

perl>  @array_of_arrays = ( [ @array_1 ], [ @array_2 ], [ @array_3 ] );

perl>  print "Array of arrays length is: " . scalar (@array_of_arrays) . "\n" ;

Accessing sub-arrays - What will and will not work

perl>  print "$array_of_arrays[0]\n" ;

perl>  print "@array_of_arrays[0]\n" ;

perl>  print "@{ $array_of_arrays[0] }\n" ;

perl>  print "First sub-array length is " . scalar (@{ array_of_arrays[0] }) ;

perl>  print "@{ $array_of_arrays[1] }\n" ;

perl>  print "@{ $array_of_arrays[2] }\n" ;

perl>  foreach $inner_array (@array_of_arrays) { print "$inner_array\n" ; }

perl>  foreach $inner_array (@array_of_arrays) { print "@{ $inner_array }\n" ; }

Printing our arrays of arrays

perl>  print "Array of arrays length: " . scalar (@array_of_arrays) . "\n" ; foreach $inner_array (@array_of_arrays) { @arr = @{ $inner_array } ; print "Sub-array length is " . scalar (@arr) . " - " . join (", " , @arr) . "\n" ; }

Encapsulate previous inside a subroutine

perl>  sub arr_display { print "Array of arrays length: " . scalar (@array_of_arrays) . "\n" ; foreach $inner_array (@array_of_arrays) { @arr = @{ $inner_array } ; print "Sub-array length is " . scalar (@arr) . " - " . join (", " , @arr) . "\n" ; } }

Alterations to outer vs. inner arrays - pay attention to the difference!

perl>  push @{ $array_of_arrays[0] } , "wilma"; push @{ $array_of_arrays[0] } , "betty";

perl>  arr_display();

perl>  pop @{ $array_of_arrays[1] } ; pop @{ $array_of_arrays[1] } ; 

perl>  arr_display();

perl>  push @array_of_arrays, [ "peter", "lois", "brian", "chris", "meg" ];

perl>  arr_display();

perl>  shift @array_of_arrays; 

perl>  arr_display();

perl>  unshift @{ $array_of_arrays[0] }, "rosie";

perl>  arr_display();

perl>  unshift @array_of_arrays, [ "eric", "kyle", "cartman", "kenny", ];

perl>  arr_display();

Hash of arrays

perl>  %hash_of_arrays = ( 'flintstones', [ "fred", "barney" ], 'jetsons', [ "george", "jane", "elroy" ], 'simpsons', [ "homer", "marge", "bart" ] ) ;

perl>  foreach $key (keys(%hash_of_arrays)) {  print "$key\n"; }

perl>  while (($key, $value) = each (%hash_of_arrays)) { print "$key: $value\n" ; }

perl>  while (($key, $value) = each (%hash_of_arrays)) { print "$key: @{ $value }\n" ; }

perl>  print "$hash_of_arrays{flintstones}\n" ;

perl>  print "@hash_of_arrays{flintstones}\n" ;

perl>  print "@{ $hash_of_arrays{flintstones} }\n" ;

perl>  print "\"flintstones\" array length is " . scalar (@{ $hash_of_arrays{flintstones} }) ;

perl>  @jetsons_array = @{ $hash_of_arrays{jetsons} };

perl>  foreach $value (@jetsons_array) { print "$value\n"; }

Hash display subroutine

perl>  sub hash_display { print "Keys in hash of arrays: " . join (", ", keys (%hash_of_arrays)) . "\n\n" ; while (($key, $value) = each (%hash_of_arrays)) { @arr = @{ $value } ; print "\"$key\" array length is " . scalar (@arr) . " - " . join (", " , @arr) . "\n" ; } }

Alterations to the hash vs. the inner arrays - pay attention to the difference!

perl>  push @{ $hash_of_arrays{flintstones} } , "wilma"; push @{ $hash_of_arrays{flintstones} } , "betty";

perl>  hash_display();

perl>  pop @{ $hash_of_arrays{jetsons} } ; pop @{ $hash_of_arrays{jetsons} } ; 

perl>  hash_display();

perl>  $hash_of_arrays{'griffins'} = [ "peter", "lois", "brian", "chris", "meg" ];

perl>  hash_display();

perl>  delete $hash_of_arrays{flintstones}; 

perl>  hash_display();

perl>  unshift @{ $hash_of_arrays{jetsons} }, "rosie";

perl>  hash_display();

perl>  $hash_of_arrays{'southpark'} = [ "eric", "kyle", "cartman", "kenny", ];

perl>  hash_display();

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.

Subroutines with neater formatting

(Code in exercise above lacks newlines because of perlsession. This is how the code could look with neater formatting.)

sub arr_display {

    print "Array of arrays length: " . scalar (@array_of_arrays) . "\n" ;
    foreach $inner_array (@array_of_arrays) {

        @arr = @{ $inner_array } ; 
        print "Sub-array length is " . scalar (@arr) . " - " . join (", " , @arr) . "\n" ;

    } 

}

sub hash_display {

    print "Keys in hash of arrays: " . join (", ", keys (%hash_of_arrays)) . "\n\n" ;
    while (($key, $value) = each (%hash_of_arrays)) {

        @arr = @{ $value } ; 
        print "\"$key\" array length is " . scalar (@arr) . " - " . join (", " , @arr) . "\n" ; 

    } 

}

IT 441: Network Services Administration Class #15 Exercise Complete by: 4/20/2018