IT 244: Introduction to Linux/Unix
Class 12 Exercise, March 30th/April 1st

Log in to pe15

• 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

(When you are ready for me to check this exercise, please scroll back up to where you entered these commands!)

• Go to your ex directory

      cd  ~/it244/ex

• Create an ex12 directory
  

      mkdir  ex12

• Go to your ex12 directory
  

      cd  ex12

Start Up a Script Session

Execute the script command, using the --flush option

    script --flush

Redirecting Input

• Make sure you are in the ex12 directory
  

      pwd

• Copy the program repeat.sh from my course_files/it244_files directory to your ex12 directory
  

      cp  ~ckelly/course_files/it244_files/repeat.sh  .

• Copy the text file foo.txt from the course_files/it244_files directory to your ex12 directory
  

      cp  ~ckelly/course_files/it244_files/foo.txt  .

• Make sure the copy operation worked
  

      ls

• Run the program repeat.sh
  

      ./repeat.sh

  Enter several lines of text, then type "X" and hit Enter.
  
  This program simply prints whatever input it receives to standard output.
  
  
• Look at the contents of foo.txt
  

      cat foo.txt

• Run the same program taking input from a file
  

      ./repeat.sh < foo.txt

  repeat.sh took its input from the file foo.txt and printed each line on the screen.

Redirecting Output

• Create a file containing information on those connected to pe15
  

      who > current_pe15.txt

• Display the contents of the file you just created
  

      cat current_pe15.txt

• Create a file containing a listing of all the files in my home directory
  

      ls ~ckelly > ck_dir.txt

• Display the contents of the file you just created
  

      cat ck_dir.txt

Appending Output to a File

• Use echo to send a string to a file.
  

      echo foo > lines.txt

• Use cat to display the contents of lines.txt
  

      cat lines.txt

  Notice that the previous contents of lines.txt have vanished.
  
  
• Send another line to lines.txt
  

      echo bar >> lines.txt

• Use cat to display the contents of lines.txt
  

      cat lines.txt

  Notice that your first line is still there.
  
  

/dev/null

• Use echo to display a string in your terminal session window
  

      echo bletch

• Now perform the same operation, but send output to /dev/null
  

      echo bletch > /dev/null

  Nothing appears in the terminal window since you have sent the string "bletch" into oblivion by redirecting the output of echo to /dev/null.

Exit Your Script Session

Use the exit command

    exit

You should see a confirmation message confirming that the script is finished, resulting in a file called typescript

Bash Script for this Exercise

• Make sure you are in your ex12 directory
  

      pwd

  If not, see me.
  
  
• Create the script ex12.sh
  

      nano  ex12.sh

• Write into this file the commands from certain sections above
  
  Enter all commands from the section Redirecting output to the section /dev/null
  
  Do not enter commands from the section Redirecting input
  
  
• Save this file
  
  Save and quit.
  
  
• Make this file executable
  

      chmod 755 ex12.sh

• Test the script
  

      ./ex12.sh

  Fix any errors you find.
  
  If you have trouble, see me.