IT 244: Introduction to Linux/Unix
Class 7 Exercise, Tuesday, February 18th

Log in to users

• 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 Ynix 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

(If you did not complete Exercise #06 during the previous class, please consult with me before continuing!)

• Make sure you are in your home directory
  

      cd

• Go to your it244 directory

      cd  it244

• Go to your ex directory
  

      cd  ex

• Create an ex07 directory
  

      mkdir  ex07

• Go to your ex07 directory
  

      cd  ex07

Experiment with Special Characters

• Try using  &  in a directory name

      mkdir  abc&def

  You should get an error message
• Look at the results
  

      ls

  mkdir created an abc directory and then tried to execute the non-existent command def
• Remove the abc directory

      rmdir abc

• Check that the abc directory is gone
  

      ls

• Use the backslash,  \  , to continue a command onto the next line

      echo foo \[Enter]
      bar [Enter]

  There should be no space between the  \  and the newline created by the Enter key.
  
  The shell did not process what you entered on the first line after you pressed the Enter key for the first time, it just gave you a new line.
  
  The backslash,  \  , turned off the special meaning of the newline character.

Create a typescript File

• Make sure you are in your ex07 directory
  

      pwd

  If the result of running this command is not

      ~YOUR_UNIX_USERNAME/it244/ex/ex07

  where YOUR_UNIX_USERNAME is the name you created for your Unix account, see me.
• Run the script command
  

      script --flush

  This will create a typescript file in your ex07 directory.
  
  You must perform the remaining steps in this exercise while script is still running.
  
  If you make a mistake, simply try again.
  
  Do not exit the script session until directed to do so...

Working with ls

• Move to your home directory

      cd

• Make sure you are in your home directory

      pwd

• Run ls without options or arguments

      ls

  You see only the visible files in your home directory
• Look at the contents of your it244 directory

      ls  it244

• Look at all the files in your home directory

      ls  -a

• Get a long listing of all the files in your home directory

      ls  -al

  Notice that you can use more than one option at a time.

cat

• Run cat on your .bash_history file

      cat  .bash_history

• Now run cat showing line numbers

      cat  -n  .bash_history

mkdir

• Go to your ex07 directory

      cd  it244/ex/ex07
      pwd

• Create a test directory

      mkdir  test

• Make sure the directory was created
  

      ls

• Create a test2 directory

      mkdir test2

• Look at the contents of your current directory

      ls

  You should see the a new test2 directory

Experiment with rm

• Move to your test2 directory

      cd  test2

• Create some files in this directory

      touch  foo  bar  bletch  gobble

  touch will create a file if it doesn't already exist.
  
  That is not its primary purpose, but we'll only be using it in this way for this class.
• Perform a long listing of the contents of the test2 directory

      ls  -l

  The first entry after -rw-r--r-- for each file is a 1. This means the files are one byte long, essentially empty.
  
  touch creates empty files.
• Remove the file foo

      rm foo

• Look at the directory contents

      ls

• Remove bar and bletch

      rm  bar  bletch

• List the contents of your current directory

      ls

  All the three files you removed should be gone.
• Remove a file using the -i option

      rm  -i  gobble

  Enter y when prompted
• Create some more empty files

      touch  baloney  ham  cheese  turkey

• Look at the directory contents

      ls

  You should see the files you just created.
• Remove all files from your current directory

      rm  *

• Look at the directory contents

      ls

  The directory should be empty

rmdir

• Make sure you are in your test2 directory

      pwd

  If not, go there.
• Create some files

      touch  red  blue  green  orange

• Move back up to the ex07 directory

      cd  ..

• Examine the contents of the test2 directory

      ls test2

• Try to remove the test2 directory using rmdir

      rmdir test2

  You should get an error message because the directory is not empty
• Look at the contents of your ex07 directory

      ls

  The test2 directory is still there.
• Remove the files in test2

      rm  test2/*

• Remove the test2 directory

      rmdir  test2

• Examine the contents of your ex07 directory
  

      ls

  The test2 directory should be gone

Run cp to Copy Files and Directories

• Create a file
  

      touch  foo

• Copy a file

      cp  foo  footoyou

• Look at the contents of the directory

      ls

• Go to the test directory

      cd test

• Create some files in this directory
  

      touch  foo  bar  bletch

• Go back to the ex07 directory
  

      cd ..

• Copy a directory

      cp  -r  test  test3

• Look at the contents of the ex07 directory

      ls

  You should see a new test3 directory
• Look at the contents of test3

      ls  test3

  It should be the same as test

mv

• Go into the test3 directory

      cd  test3

• Change the name of footoyou

      mv  foo  foo_to_you

• Examine the changes

      ls

• Move a file to another directory

      mv foo_to_you ../test

• Look at the contents of the current directory

      ls

  foo_to_you is no longer in your current directory
• Look at the contents of your test directory

      ls ../test

  foo_to_you has been moved to the test directory

End your script Session

• Exit from your script session
  

      exit

If you hadn't used the "flush" option, you would need to do this or the typescript file would never be created
• Look at the contents of the typescript file
  

      cat  typescript

Working with Pagers

• Use cat on the exercise #05 page

      cat  /home/ckelly/public_html/teaching/common/exercises/linux/intro/exercise_05.html

  Scroll back up in your terminal session to see the beginning of the file.
  
  
• Use more on the same file

      more  /home/ckelly/public_html/teaching/common/exercises/linux/intro/exercise_05.html

• Move down one screen

      Space

• Look at the more help section

      h

• Use the Enter key to moves down a few lines

      Enter
      Enter
      Enter

• Move to the end of the file
  
  Hit Space as many times as you need to.
  
  You should reach the end of the file and exit more.
  
  
• Use less on the same file

      less  /home/ckelly/public_html/teaching/common/exercises/linux/intro/exercise_05.html

• Move to the end of the file
  
  Hit Space until you reach the end of the file.
  
  You see (END) but you are still in less.
  
  
• Examine the help section

      h

• Quit the help section

      q

  Hitting q the first time only gets you out of the help section.
  
  
• Quit less

      q

  Hitting q the second time only gets you out of less.

Filename Completion

• Create the directory test

      mkdir  test

• Move to the test directory

      cd  test

• Create some files

      touch  foo  foobar  foobletch  bletch

• Use filename complete to run ls on bletch

      ls  ble[Tab][Enter]

• Use filename completion to see all files with "foo" in the name

      ls  foo[Tab][Tab]

  After the first Tab, you should hear a beep. After the second, all files beginning with "foo" should be displayed.
  
  
• Keep typing to run ls on foobletch

      bl[Tab][Enter]

  As you supply more letters in the filename, the completion mechanism narrows down the possibilities.
  
  

Reopen typescript File

• Make sure you are in your ex07 directory
  

      pwd

  If the result of running this command is not

      ~YOUR_UNIX_USERNAME/it244/ex/ex07

  where YOUR_UNIX_USERNAME is the name you created for your Unix account, see me.
• Run the script command
  

      script --flush --append

  This will reopen the typescript file in your ex07 directory, with appending.
  
  Do not exit the script session until instructed to do so.

Experimenting with echo

• Run echo with a string argument

      echo  foo  bar  bletch

• Run echo using the -n option

      echo  -n  foo  bar  bletch

  Notice that "foo bar bletch" appears before the normal prompt.
  
  That is because the -n option turned off sending a newline character to advance to the next line.
  
  
• Use echo to display a system variable

      echo  SHELL:  $SHELL

• You must use a $ when displaying the value of a variable

      echo SHELL:  SHELL

hostname

• Determine the name of your current host

      hostname

• Determine the IP address of your current host

      hostname  -i

grep

• Go to the it244_files directory
  

      cd   /home/ckelly/course_files/it244_files

• Look at the contents of foo.txt
  

      cat  foo.txt

• Look for lines with the string "foo" in foo.txt
  

      grep  foo  foo.txt

• Experiment with the -i option
  
  First look for "bar" without the -i option

      grep  bar  foo.txt

  Now try the same search with -i

      grep  -i  bar  foo.txt

• Use grep with the -r option
  
  grep, when used with the -r option, looks in all subdirectories of the directory given to it as its second argument

      grep  -r  foo  .

  The . means the current directory.
  
  Everything up to the colon, : , is the path to the file in which the string was found.
  
  The text after the colon is the line itself.
  
  The entries in the directory .svn are associated with the versioning software, subversion, I use in all my work.
  
  
• Use grep -v to remove unwanted lines
  
  Many of the lines returned in the previous invocation of grep come from files with the string "svn" in their file names.
  
  These are files created by subversion.
  
  Let's remove these lines grep twice, using a pipe, |, to feed the output of the first invocation of grep into the input of the second

      grep  -r  foo  .  |  grep  -v  svn

  Notice that all the entries in the subversion files have been removed.
  
  We'll discuss pipes in a future class.

head

• Display the contents of red_sox.txt

      cat  red_sox.txt

• Display the first 10 lines of red_sox.txt

      head  red_sox.txt

• Display the first line of red_sox.txt

      head  -1  red_sox.txt

tail

• Display the last 10 lines of red_sox.txt

      tail  red_sox.txt

• Display the last two lines of red_sox.txt

      tail  -2 red_sox.txt

sort

• Look at fruit.txt

      cat  fruit.txt

• Run sort on this file

      sort  fruit.txt

• Sort this file in reverse alphabetical order

      sort  -r  fruit.txt

• Look at numbers1.txt

      cat  numbers1.txt

• Run sort on this file without any options

      sort  numbers1.txt

  Since the numbers from 10 to 19 begin with a 1 they appear before 2
  
  
• Sort numbers1.txt in numerical order

      sort  -n  numbers1.txt

• Sort numbers1.txt in reverse numerical order

      sort  -nr  numbers1.txt

  Note that sort allows you to combine options after the dash.

diff

• Examine the contents of numbers1.txt and numbers2.txt

      cat  numbers1.txt
      cat  numbers2.txt

• Use diff to compare numbers1.txt and numbers2.txt

      diff  numbers1.txt  numbers2.txt

  The output is hard to read, because it contains instructions for the Unix patch utility to convert the first file given at the command line to the second.
  
  
• Use the -y option to diff to create readable output

      diff  -y  numbers1.txt  numbers2.txt

  This output is much easier to read.

End your script Session

• Exit from your script session
  

      exit

If you hadn't used the "flush" option, you would need to do this or the typescript file would never be created
• Look at the contents of the typescript file
  

      cat  typescript

Create a Bash script

• Go to your home directory
  

      cd

• Go to your it244 directory
  

      cd  it244

• Go to your ex directory
  

      cd  ex

• Go to your ex07 directory
  

      cd  ex07

• Create the script file ex07.sh
  

      nano  ex07.sh

• Write into this file commands from certain of the sections above
  
  Go back to the section of this Class Exercise called Experimenting with echo.
  
  Enter all the commands from the echo section to the section called diff into this script file.
  
  Do not run the more or less commands inside ex07.sh
  
  Do not use Tab completion inside ex07.sh
  
  You do not have to use echo in scripts for the Class Exercise.
  
  
• Save and quit
  
  
  
• Run this script
  

      bash  ex07.sh