• 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, October 1st 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 ""
  
  line_1 = "8765.1.87654.654321  --  123.134.32.5  [18-03-2021] [00:03:21] GET  /12_exercise_it116.html  HTTP/1.1 200 56810323"
  line_2 = "Accepted password for pe15 on Oct 25 2021 from 197.81.14.23 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 ", test_regular_expression(regex_1, line_1))
  print("regex_2",  regex_2, "\t ", test_regular_expression(regex_2, line_1))
  print("regex_3",  regex_3, "\t ", test_regular_expression(regex_3, line_1))
  print("regex_4",  regex_4, "\t ", test_regular_expression(regex_4, line_1))
  print("regex_5",  regex_5, "\t ", test_regular_expression(regex_5, line_1))
  print("regex_6",  regex_6, "\t ", test_regular_expression(regex_6, line_1))
  print("regex_7",  regex_7, "\t ", test_regular_expression(regex_7, line_2))
  print("regex_8",  regex_8, "\t ", test_regular_expression(regex_8, line_2))
  print("regex_9",  regex_9, "\t ", test_regular_expression(regex_9, line_2))
  print("regex_10", regex_10,"\t ", 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	Hostname	line_2
  regex_8	Month	line_2
  regex_9	Year	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

  123.134.32.5
  18
  03
  2021
  00:03:21
  12_exercise_it116.html
  pe15
  Oct
  2021
  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

  123.134.32.5
  18
  03
  2021
  00:03:21
  12_exercise_it116.html
  pe15
  Oct
  2021
  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

  123.134.32.5
  18
  03
  2021
  00:03:21
  12_exercise_it116.html
  pe15
  Oct
  2021
  60695

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