• 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 30th 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(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 ""
    
  auth_log_line = "Mar 16 11:58:13 it20 sshd[12041]: Accepted password for it341 from 65.96.149.57 port 60695 ssh2"
  apache_log_line = "205.236.184.32 - - [09/Mar/2014:00:03:21 +0000] 'GET /wzbc-2014-03-05-14-00.mp3 HTTP/1.1' 200 56810323"
  
  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,  auth_log_line))
  print("regex_2 :",  regex_2,  "\t returned ", test_regular_expression(regex_2,  auth_log_line))
  print("regex_3 :",  regex_3,  "\t returned ", test_regular_expression(regex_3,  auth_log_line))
  print("regex_4 :",  regex_4,  "\t returned ", test_regular_expression(regex_4,  auth_log_line))
  print("regex_5 :",  regex_5,  "\t returned ", test_regular_expression(regex_5,  auth_log_line))
  print("regex_6 :",  regex_6,  "\t returned ", test_regular_expression(regex_6,  auth_log_line))
  print("regex_7 :",  regex_7,  "\t returned ", test_regular_expression(regex_7,  auth_log_line))
  print("regex_8 :",  regex_8,  "\t returned ", test_regular_expression(regex_8,  apache_log_line))
  print("regex_9 :",  regex_9,  "\t returned ", test_regular_expression(regex_9,  apache_log_line))
  print("regex_10:",  regex_10, "\t returned ", test_regular_expression(regex_10, apache_log_line))
  

Specification

• Define the variables below

  Variable	Should Return	From String	May Use Literals
  regex_1	Month name and day number	auth_log_line
  regex_2	Hours, minutes, seconds	auth_log_line	:
  regex_3	The hostname, e.g. it20	auth_log_line	: sshd
  regex_4	The number in square brackets after "sshd"	auth_log_line	sshd
  regex_5	The account name, e.g. it341	auth_log_line	for
  regex_6	IP address	auth_log_line	.
  regex_7	Port number	auth_log_line	port
  regex_8	IP address	apache_log_line	.
  regex_9	Date	apache_log_line	/
  regex_10	The file requested	apache_log_line	GET

• The only string literals you can use in your regular expressions are those in the last column
• So you cannot use "(Mar)" to match the month name in auth_log_line in the variable regex_1
• But you can use ": sshd" In the value for regex_3
• 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

  Mar 16
  11:58:13
  it20
  12041
  it341
  65.96.149.57
  60695
  205.236.184.32
  09/Mar/2014
  /wzbc-2014-03-05-14-00.mp3

Suggestions

• Write this script in stages
• Test your script at each step
• Start by puting 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
• 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

  Mar 16
  11:58:13
  it20
  12041
  it341
  65.96.149.57
  60695
  205.236.184.32
  09/Mar/2014
  /wzbc-2014-03-05-14-00.mp3

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

• 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

  Mar 16
  11:58:13
  it20
  12041
  it341
  65.96.149.57
  60695
  205.236.184.32
  09/Mar/2014
  /wzbc-2014-03-05-14-00.mp3

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