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Basic Regular Expressions
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Basic Regular Expressions

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Transcript

  • 1. Regular Expressions What are they and what can they do for you?Thursday, February 7, 13
  • 2. b[A-Z0-9._%+-]+@[A- Z0-9.-]+.[A-Z]{2-4}b Source: http:/ /www.regular- expressions.info/email.htmlThursday, February 7, 13
  • 3. So...what is a regular expression?Thursday, February 7, 13
  • 4. A Regular Expression is a pattern for a string.Thursday, February 7, 13
  • 5. What can you do with Regular Expressions? Test a string Extract a string Change a stringThursday, February 7, 13
  • 6. Creating Regular Expressions /RegularExpression/Thursday, February 7, 13
  • 7. Scenario #1 Testing StringsThursday, February 7, 13
  • 8. Examples from “Programming Ruby” (PickAxe)Thursday, February 7, 13
  • 9. “dog and cat”Thursday, February 7, 13
  • 10. “dog and cat” /cat/Thursday, February 7, 13
  • 11. “dog and cat” /cat/ /cat/ =~ “dog and cat”Thursday, February 7, 13
  • 12. =~ /cat/ =~ “dog and cat”Thursday, February 7, 13
  • 13. Thursday, February 7, 13
  • 14. Thursday, February 7, 13
  • 15. match /cat/.match(“dog and cat”)Thursday, February 7, 13
  • 16. Valid EmailsThursday, February 7, 13
  • 17. thing@thing.thingThursday, February 7, 13
  • 18. RubularThursday, February 7, 13
  • 19. Alternation /Nell | Brandon/Thursday, February 7, 13
  • 20. . Metacharacters any single character character can appear * any number of timesThursday, February 7, 13
  • 21. /.*/ matches ANYTHINGThursday, February 7, 13
  • 22. Range [a-d] [1-4]Thursday, February 7, 13
  • 23. Shorthand! w stands for any word character. It’s the same as: [a-zA-Z0-9_]Thursday, February 7, 13
  • 24. Metacharacters + character occurs one or more timesThursday, February 7, 13
  • 25. Thursday, February 7, 13
  • 26. Scenario #2 Extracting StringsThursday, February 7, 13
  • 27. Shorthand! d stands for any digit D stands for any non- digitThursday, February 7, 13
  • 28. Repetition! d{3} Looks for exactly 3 digitsThursday, February 7, 13
  • 29. Make It Optional! ? Makes a character optional. It can occur 0 or 1 time.Thursday, February 7, 13
  • 30. Scenario #3 Changing StringsThursday, February 7, 13
  • 31. “Brandon is the teacher of the class right now. Brandon is teaching about regular expressions.”Thursday, February 7, 13
  • 32. sub(/pattern/, “text”)Thursday, February 7, 13
  • 33. gsub(/pattern/, “text”) (replace ALL the matches)Thursday, February 7, 13
  • 34. sub and gsub create new strings. sub! and gsub! change the original stringsThursday, February 7, 13
  • 35. Welcome to the wonderful world of Regular Expressions!Thursday, February 7, 13