CP215 Application Design

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Randolf Reeves
6 years ago
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1 CP215 Application Design

2 Microsoft HoloLens developer preorder: $3,000 Tech News!

3 Tech News! Microsoft HoloLens developer preorder: $3,000 Raspberry Pi 3 with Wi-Fi and Bluetooth built-in: $35

4 Hacker's Tip of the Day Obey the rule of Generation Avoid hand-hacking!

5 Hacker's Tip of the Day Obey the rule of Generation Avoid hand-hacking! Automate configuration file creation Write programs that generate other programs

6 Version Control myfile.py def multiply(a, b): result = 0 for i in range(a): for j in range(b): result += 1 return result

7 Version Control myfile.py def multiply(a, b): result = 0 for i in range(a): for j in range(b): result += 1 return result myfile2.py def multiply(a, b): result = 0 for i in range(a): result += b return result

8 Version Control myfile.py def multiply(a, b): result = 0 for i in range(a): for j in range(b): result += 1 return result myfile3.py def multiply(a, b): result = -1 for i in range(a): result += b return result myfile2.py def multiply(a, b): result = 1 for i in range(a): result += b return result myfile4.py def multiply(a, b): '''Multiply the numbers!''' result = 0 for i in range(a): result += b return result myfile5.py def multiply(a, b): '''Multiply the numbers!''' return a * b * 2

9 Centralized Version Control Systems (CVS, SVN) User1 Working Copy User3 Working Copy Central Repository User2 Working Copy User4 Working Copy

10 Centralized Version Control Systems 1. Checkout a working copy of the code from the central repository 2. Make changes to files. Fix bugs. Add features. 3. Commit changes to repository. 4. Other users update to get your new changes.

11 Centralized Version Control Systems 1. Add new files to your working copy and then commit them 2. Branch the main line of the repository 3. Merge changes between concurrent user updates or branches

12 Distributed Version Control Systems (git, Mercurial, BitKeeper) User1 Copy User3 Copy User2 Copy User4 Copy User4 Copy

13 Git Existing Repository 1. Clone a working copy of the code from somewhere 2. Make changes to files. Fix bugs. Add features. 3. Commit changes to repository. 4. Other users pull to get your new changes.

14 Git Existing Repository 1. git clone <URL> 2. Make changes to files git add file.py 4. git commit -m message describing changes 5. git push origin master

15 GitHub

16 Dynamic Web Pages Client Code can run in the browser (or in a browser plugin) Server Code runs on the server machine and sends back HTML that was dynamically generated.

17 Dynamic Web Pages Client Code can run in the browser (or in a browser plugin) Server Code runs on the server machine and sends back HTML that was dynamically generated.

18 Client's Perspective GET /cgi-bin/hello.cgi HTTP/1.1 Client Server

19 Client's Perspective Just a normal URL request. GET /cgi-bin/hello.cgi HTTP/1.1 Client Server

20 Client's Perspective Client Get back a normal HTML page: <html> <body> Hello, ! </body> </html> Server

21 Client's Perspective This would change for each different client. Get back a normal HTML page: Client <html> <body> Hello, ! </body> </html> Server

22 Client's Perspective Client Get back a normal HTML page: <html> <body> Hello, ! </body> </html> Server

23 Server's Perspective GET /cgi-bin/hello.cgi HTTP/1.1 Client Server

24 hello.cgi is located in the special cgibin directory. Server's Perspective GET /cgi-bin/hello.cgi HTTP/1.1 Client Server

25 Server's Perspective hello.cgi is an executable. GET /cgi-bin/hello.cgi HTTP/1.1 Client Server

26 I'll execute the file and send back to the client any output. Server's Perspective GET /cgi-bin/hello.cgi HTTP/1.1 Client Server

27 Unix/Linux Executable Script: hello Hello, world!

29 Unix/Linux Executable Script: hello Hello, world! Change permissions of hello. What permissions?

30 Unix/Linux Executable Script: hello Hello, world! Let's try 755.

32 Unix/Linux Executable Script: hello #! /usr/bin/env python print Hello, world!

33 CGI Script: hello.cgi #! /usr/bin/env python print "Content-type:text/html\r\n\r\n" print "Hello, World!"

34 CGI Script: hello.cgi #! /usr/bin/env python print "Content-type:text/html\r\n\r\n" print "Hello, World!" What does this line look like?

35 Broken CGI Script #! /usr/bin/env python print "Content-type:text/html\r\n\r\n" print "Hello, World!

36 Broken CGI Script #! /usr/bin/env python print "Content-type:text/html\r\n\r\n" print "Hello, World! Missing closing quotation mark.

37 Broken CGI Script 500 Internal Server Error Client Server <html> <body> Oh, no! An error has occurred! </body> </html>

38 /var/log/apache2/error.log #0 /fav.ico: Missing file. #1 /cgi-bin/hello.cgi (Line 3): print Hello, World! ^ SyntaxError: EOL while scanning string literal

39 Sending User Input to CGI <html> <body> <form name= input action="/cgi-bin/login.cgi" method="get"> First name: <input type="text" name="firstname" /><br /> Last name: <input type="text" name="lastname" /><br /> <input type="submit" value="submit" /> </form> </body> </html>

40 /cgi-bin/login.cgi?firstname=matthew&lastname=whitehead

41 login.cgi #! /usr/bin/env python # Import modules for CGI handling import cgi, cgitb # Create instance of FieldStorage form = cgi.fieldstorage() # Get data from fields firstname = form.getvalue('firstname') lastname = form.getvalue('lastname') print "Content-type:text/html\r\n\r\n" print "Hi, %s %s!" % (firstname, lastname)

42 Environment Variables #! /usr/bin/env python import os # Import modules for CGI handling import cgi, cgitb print "Content-type:text/html\r\n\r\n" print "Your IP address is %s" % (os.environ['remote_addr']) print "Your browser is %s" % (os.environ['http_user_agent'])

43 Break!

NETB 329 Lecture 13 Python CGI Programming

NETB 329 Lecture 13 Python CGI Programming 1 of 83 What is CGI? The Common Gateway Interface, or CGI, is a set of standards that define how information is exchanged between the web server and a custom