1. 20-753: Fundamentals of Web Programming 1 Lecture 10: Server-Side Scripting II Fundamentals of Web Programming Lecture 10: Server-Side Scripting II

2. 20-753: Fundamentals of Web Programming 2 Lecture 10: Server-Side Scripting II Announcements Your Feedback is Welcome –Feel free to send email with your comments, questions, suggestions, etc. on the course so far –Some students have expressed a need for more fundamentals on programming and operating systems

3. 20-753: Fundamentals of Web Programming 3 Lecture 10: Server-Side Scripting II Announcements Upcoming Recitations –After class (3pm-4pm) –Optional (intended for those with less programming experience) –Format: informal lectures & hands-on practice –Topics Fri 6/4: Programming Basics Mon 6/7: Operating Systems Basics

4. 20-753: Fundamentals of Web Programming 4 Lecture 10: Server-Side Scripting II Today’s Topics Regular Expressions in PERL String Operations: –Pattern Matching –Substitution Examples of Pattern Matching Putting It Together: An Automated Link Tester

5. 20-753: Fundamentals of Web Programming 5 Lecture 10: Server-Side Scripting II Regular Expressions Chapter 7 in ‘Learning Perl’ A pattern to be matched against a string Match may assign values to match variables Match may be used to replace parts of a string (substitution)

6. 20-753: Fundamentals of Web Programming 6 Lecture 10: Server-Side Scripting II Regular Expressions Used by many programs (Unix commands, shells, etc.) Useful for processing text files E.g., web pages –matching links –matching particular tags, tag contents –etc.

7. 20-753: Fundamentals of Web Programming 7 Lecture 10: Server-Side Scripting II Simple Examples print if ($line =~ /abc/); # exact match print if ($line =~ /ab*c/); # zero or more b’s

8. 20-753: Fundamentals of Web Programming 8 Lecture 10: Server-Side Scripting II Character Classes [abcde] # match one of them [a-z] # specify a range [^a-z] # can be negated

9. 20-753: Fundamentals of Web Programming 9 Lecture 10: Server-Side Scripting II Predefined Classes ElementEquivalentNegation \d (digit)[0-9]\D \w (word char)[a-zA-Z0-9_]\W \s (space char)[ \r\t\n\f]\S. (any char)[^\n]\n Classes can be combined; e.g.: [\da-fA-F] # one hex digit

10. 20-753: Fundamentals of Web Programming 10 Lecture 10: Server-Side Scripting II Multipliers OperatorMeaning *“zero or more” +“one or more” ?“zero or one” Examples: –\d*a? –[a-zA-Z\.]+

11. 20-753: Fundamentals of Web Programming 11 Lecture 10: Server-Side Scripting II Multipliers General Multipliers –x{a,b}# between a and b x’s –x{5,} # 5 or more x’s –x{0,5}# 0 to 5 x’s –x{5}# exactly 5 x’s

12. 20-753: Fundamentals of Web Programming 12 Lecture 10: Server-Side Scripting II Matches with Memory Parts of a pattern match can be saved by using parenthesis to enclose parts of the pattern Example: /a(b+)c/ The result is stored in $1, $2, etc. (you can have >1 memory variable)

13. 20-753: Fundamentals of Web Programming 13 Lecture 10: Server-Side Scripting II Patterns are Greedy Patterns match the maximum number of characters possible Example: $line = “fred xxxxxx barney”; $line =~ /(x+)/; print “$1\n”; Output: xxxxxx

14. 20-753: Fundamentals of Web Programming 14 Lecture 10: Server-Side Scripting II Anchors /^abc/# start of line /abc$/# end of line /abc\b/# word boundary

15. 20-753: Fundamentals of Web Programming 15 Lecture 10: Server-Side Scripting II Pattern Match Examples Sample program which shows the results of various patterns: findpat.cgi findpat.cgi

16. 20-753: Fundamentals of Web Programming 16 Lecture 10: Server-Side Scripting II Substitutions Two regular expressions –what to match –what to substitute Examples: –s/test/quiz/; –s| (.*) |$1|;

17. 20-753: Fundamentals of Web Programming 17 Lecture 10: Server-Side Scripting II Putting It Together Automated Link Tester –Input: a URL –Output: an HTML page that lists all the links from that page –recursively follow links to subpages and search them, too –print “OK” if the link points to a page, “NOT FOUND” otherwise

18. 20-753: Fundamentals of Web Programming 18 Lecture 10: Server-Side Scripting II Example Program testlinks.html