• Due
• What You Need to Do
• Setup On Your Machine
• What is Special About This Assignment
• Additional Setup
• Specification
• Output
• Suggestions
• Testing on Your Machine
• Copy the Script to Unix
• Testing the Script on Unix (Optional)

Due

Sunday, March 22nd at 11:59 PM

What You Need to Do

• Create the script hw7.py
• Make sure it obeys the rules in Rules for Homework Scripts
• Make sure the script has a hashbang line and is executable
• Move it to an an hw7 directory on pe15.cs.umb.edu

Setup On Your Machine

• Open a text editor.
  I would suggest the text editor built into the program IDLE.
• Save the file as hw7.py

What is Special About This Assignment

• This assignment is going to be different from the other homework assignments
• You will have to do very little coding for this script
• Instead, I will give you a function that will test regular expressions
• You will add this function to your script
• You will then assign values to 10 variables
• The values of these variables will be regular expressions
• Each of these values will match a string and extract a value
• The string and the value are specified below

Additional Setup

• Copy the following statements into your hw7.py script

  import re
  
  def test_regular_expression(regex, test_string) :
      pattern = re.compile(r'' + regex )
      match   = pattern.search(test_string)
      if match :
          try :
              return match.group(1)
          except :
              print('Match found but no substring returned')
              return ''
      else:
          print(regex, 'does not match', test_string)
          return ''
  
  line_1 = "123.134.32.12 - - [12/Feb/2016:00:03:21 +0000] GET 08_exercise_it117.html  HTTP/1.1 200 56810323"
  line_2  = "Mar 16 11:58:13 pe15 sshd[12041]: Accepted password for it341 from 65.96.149.57 port 60695 ssh2"
  
  regex_1  = ""
  regex_2  = ""
  regex_3  = ""
  regex_4  = ""
  regex_5  = ""
  regex_6  = ""
  regex_7  = ""
  regex_8  = ""
  regex_9  = ""
  regex_10 = ""
  
  print('regex_1',  regex_1, '\t returned ', test_regular_expression(regex_1, line_1))
  print('regex_2',  regex_2, '\t returned ', test_regular_expression(regex_2, line_1))
  print('regex_3',  regex_3, '\t returned ', test_regular_expression(regex_3, line_1))
  print('regex_4',  regex_4, '\t returned ', test_regular_expression(regex_4, line_1))
  print('regex_5',  regex_5, '\t returned ', test_regular_expression(regex_5, line_1))
  print('regex_6',  regex_6, '\t returned ', test_regular_expression(regex_6, line_1))
  print('regex_7',  regex_7, '\t returned ', test_regular_expression(regex_7, line_2))
  print('regex_8',  regex_8, '\t returned ', test_regular_expression(regex_8, line_2))
  print('regex_9',  regex_9, '\t returned ', test_regular_expression(regex_9, line_2))
  print('regex_10', regex_10,'\t returned ', test_regular_expression(regex_10,line_2))

Specification

• Define the variables below

  Variable	Value Returned	String
  regex_1	IP address	line_1
  regex_2	Day number	line_1
  regex_3	Month name	line_1
  regex_4	Year	line_1
  regex_5	Hours, minutes, seconds	line_1
  regex_6	Filename with extension	line_1
  regex_7	Month	line_2
  regex_8	Time	line_2
  regex_9	Hostname	line_2
  regex_10	Port	line_2

• You must not use any string literals inside the parentheses of your regular expressions
• Don't forget that . is a meta-character
• If you need to use it as an ordinary character you must put \ before it

Output

• The output of the script show the value of each variable so I cannot show it to you
• But I can show you what the returned values should be

  123.134.32.12
  12
  Feb
  2016
  00:03:21
  08_exercise_it117.html
  Mar
  11:58:13
  pe15
  60695

Suggestions

• Write this script in stages
• Test your script at each step
• Start by putting a # before each print statement in the test code
• Work on one variable at a time
• Remove the # from the print statement for the regex variable you are working on
• Write the regular expression that matches the value you need and put parentheses around it
• The only ordinary characters you can use are those listed in the table above
• Repeat this procedure until you have given values to all regex variables

Testing on Your Machine

• Open IDLE
• Use the Open command in IDLE to open hw7.py
• Under the Run menu, select Run Module
• I cannot show you the correct output
• Because the output would show you the regular expression
• But I can show you the values that should be returned

  123.134.32.12
  12
  Feb
  2016
  00:03:21
  08_exercise_it117.html
  Mar
  11:58:13
  60695

Copy the Script to Unix

• Open FileZilla and connect to pe15.cs.umb.edu
• Go to your it117 directory
• Go to your hw directory
• Right-click in the whitespace inside the hw directory
• Enter hw7 in the dialog box
• Click and drag your script from the bottom left panel to the bottom right panel
• Right-click on the file and select "Permissions" from the menu
• Enter 755 in the box provided
• This will make the script executable

Testing the Script on Unix (Optional)

• Connect to pe15.cs.umb.edu using an ssh client like putty.exe (Windows) or ssh (Mac)
• Go to the directory for this exercise

  cd  it117/hw/hw7

• Run this script

  hw7.py

• I cannot show you the correct output
• Because the output would show you the regular expression
• But I can show you the values that should be returned

  123.134.32.12
  12
  Feb
  2016
  00:03:21
  08_exercise_it117.html
  Mar
  11:58:13
  60695

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