IT 244: Introduction to Linux/Unix - Class 21 Exercise, Tuesday, May 11th

IT 244: Introduction to Linux/Unix
Class 21 Exercise, Tuesday, May 11th

Log in to pe15

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 pe15.

ssh configuration parameter value

protocol ssh

ssh version 2

ssh port 22

host pe15.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.

Directory for This Exercise
Go to your ex directory
    cd  ~/it244/ex
Create an ex21 directory
    mkdir  ex21
Go to your ex21 directory
    cd  ex21
Start Up a script Session

Execute the script command, using the --flush option
    script --flush
Command Line Editing
Enter a long command line
    echo foo; echo bar; echo bletch
Recover this last command line but do not hit Enter
    ↑
Go to the beginning of the command line
    Control A
Go to the end of the command line
    Control E
Go back to just before the last echo command

Use the left arrow key (←) to do this.
Remove the last echo command
    Control K
Remove the command line completely
    Control U
Command Completion
Go back to your ex21 directory
    cd ~/it244/ex/ex21
Enter the first two letters of the mkdir command then hit Tab
    mk[Tab]
The terminal should beep.
Hit Tab a second time
    [Tab]
You should now see a list of all commands that begin with "mk".
Type "di" after "mk" and hit Tab

The mkdir command is complete.

Create the directory test

Add the argument "test" after mkdir.
Pathname Completion
Go to your it244 directory using pathname completion
    cd  ~/it2[Tab]  [Enter]
You should now be in your it244 directory.
Show your current directory and it's contents
    pwd ; ls
Enter the first few letters of a pathname, then hit Tab
    cd ~/it244/e[Tab]
The Readline library adds an "x"
Hit Tab again

The Readline library adds "ex" to the pathname.

Hit the Tab twice more

The Readline library lists the example directories.

Add "21" and hit Return

This will take you back to your ex21 directory.
Variable Completion
Create the variable foo
    team='Red Sox'
Use variable completion to print the value of this variable
    echo $t[Tab][Enter]
Create two new variables
    blar=blimp ; bletch=baloney
Use variable name completion
    echo $b[Tab]
Readline completion adds an l.
Use variable completion to see your choices
[Tab][Tab]
Completion shows you the variables that match.
Exit Your script Session

Use the exit command
    exit
You should see a confirmation message confirming that the script session is finished, resulting in a file called typescript. I will look at the typescript file, along with the other files in your directory.

Aliases
Go to your home directory
    cd
Make sure you are in your home directory
    pwd
Edit .bash_profile using an editor
    nano .bash_profile
Create the global variable ex in .bash_profile
    export ex=it244/ex
Create an alias using your ex variable
    alias ex='cd $ex'
Save these changes and quit
Go to your ex21 directory
    cd  ~/it244/ex/ex21
Re-Start Your script Session Execute the script command, using both the --flush option AND the --append option
    script --flush --append
Make this change take effect
    source ~/.bash_profile
Use this alias
    ex
Display your current directory
    pwd
Exit Your script Session
Use the exit command
            exit
You should see a confirmation message confirming that the script session is finished, resulting in a file called typescript. I will look at the typescript file, along with the other files in your directory.
Go back to your home directory
    cd
Open .bash_profile in an editor
    nano .bash_profile
Create two new aliases
    alias h='history 10'
    alias hg='history | grep '
Save these changes and quit
Make sure you are inside your ex21 directory
    cd  ~/it244/ex/ex21
Re-Start Your script Session
Execute the script command, using both the --flush option AND the --append option
    script --flush --append
Make this change take effect
    source ~/.bash_profile
Run the first alias
    h
You should see your last 10 command lines.
Run the second alias
    hg cd
You should see every time you have run cd in the last 500 command lines.
Single and Double Quotes
Create a variable
    city=Boston
Display the value of this variable
    echo $city
Define another variable using single quotes
    capitol='$city is the capitol of Massachusetts'
Display the value of this variable
    echo $capitol
The variable city is not evaluated because it was enclosed in single quotes when defined.
Redefine city using double quotes
    capitol="$city is the capitol of Massachusetts"
Display this redefined variable
    echo $capitol
The double quotes permitted the shell to evaluate city when assigning a value to capitol.
Make sure you are in your home directory
    cd
Display the value of PWD
    echo $PWD
PWD has the address of your home directory.
Go to my home directory
    cd ~ckelly
Display the value of PWD
    echo $PWD
PWD is now set to the address of my home directory.
Create an alias using this variable in double quotes
    alias new_pwd="echo $PWD"
Use this alias in your current location
    new_pwd
It displays the address of my home directory.
Return to your home directory
    cd
Make sure you are in your home directory
    pwd
Use the alias in this new location
    new_pwd
The alias again returns the address of my home directory.

Since you created the alias in my home directory, and used double quotes, the value of PWD at the time of definition was used in creating the alias.

But you want alias to use the value of PWD at the time the alias is used.
Redefine the alias using single quotes
    alias new_pwd='echo $PWD'
Use the newly redefined alias
    new_pwd
It displays the address of your home directory.
Go to my home directory
    cd ~ckelly
Use the redefined alias again
    new_pwd
It displays the address of my home directory.

Since you defined the alias using single quotes, PWD was not evaluated when it was defined, but instead, when it is used.
Exit Your script Session

Use the exit command
    exit
You should see a confirmation message confirming that the script session is finished, resulting in a file called typescript. I will look at the typescript file, along with the other files in your directory.

Functions
Go to your home directory
    cd
Open .bash_profile using nano
    nano  .bash_profile
Define a function
    cheer ()
    {
        echo Go $1'!'
    }
Define another function
    print_args ()
    {
        echo "arg1: $1"
        echo "arg2: $2"
        echo "arg3: $3"
    }
Save and quit
Make sure you are inside your ex21 directory
    cd  ~/it244/ex/ex21
Re-Start Your script Session
Execute the script command, using both the --flush option AND the --append option
    script --flush --append
Make these functions available in your login shell
    source  ~/.bash_profile
Use the first function
    cheer 'Red Sox'
Use the second function
    print_args  foo  bar  bletch
Exit Your script Session

Use the exit command
    exit
You should see a confirmation message confirming that the script session is finished, resulting in a file called typescript. I will look at the typescript file, along with the other files in your directory.

Checking Your Work

Tell the instructor you have finished making changes to .bash_profile

There is no Bash script for this Class Exercise.

ssh configuration parameter	value
protocol	ssh
ssh version	2
ssh port	22
host	pe15.cs.umb.edu
user name	your Unix username
Authentication method	password

IT 244: Introduction to Linux/Unix Class 21 Exercise, Tuesday, May 11th

Log in to pe15

Directory for This Exercise

Start Up a script Session

Command Line Editing

Command Completion

Pathname Completion

Variable Completion

Exit Your script Session

Aliases

Single and Double Quotes

Exit Your script Session

Functions

Exit Your script Session

Checking Your Work

IT 244: Introduction to Linux/Unix
Class 21 Exercise, Tuesday, May 11th