1. Regular Expressions
What are they and what can they do for you?
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2. b[A-Z0-9._%+-]+@[A-
Z0-9.-]+.[A-Z]{2-4}b
Source: http:/ /www.regular-
expressions.info/email.html
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3. So...what is a
regular expression?
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4. A Regular Expression is
a pattern for a string.
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5. What can you do with
Regular Expressions?
Test a string
Extract a string
Change a string
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6. Creating Regular
Expressions
/RegularExpression/
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7. Scenario #1
Testing Strings
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8. Examples from
“Programming Ruby” (PickAxe)
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9. “dog and cat”
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10. “dog and cat”
/cat/
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11. “dog and cat”
/cat/
/cat/ =~ “dog and cat”
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12. =~
/cat/ =~ “dog and cat”
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13. Thursday, February 7, 13

14. Thursday, February 7, 13

15. match
/cat/.match(“dog and cat”)
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16. Valid Emails
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17. thing@thing.thing
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18. Rubular
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19. Alternation
/Nell | Brandon/
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20. .
Metacharacters
any single character
character can appear
* any number of times
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21. /.*/
matches ANYTHING
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22. Range
[a-d] [1-4]
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23. Shorthand!
w stands for any word
character.
It’s the same as:
[a-zA-Z0-9_]
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24. Metacharacters
+ character occurs
one or more times
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25. Thursday, February 7, 13

26. Scenario #2
Extracting Strings
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27. Shorthand!
d stands for any digit
D stands for any non-
digit
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28. Repetition!
d{3}
Looks for exactly 3 digits
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29. Make It Optional!
?
Makes a character
optional. It can occur
0 or 1 time.
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30. Scenario #3
Changing Strings
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31. “Brandon is the teacher
of the class right now.
Brandon is teaching about
regular expressions.”
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32. sub(/pattern/, “text”)
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33. gsub(/pattern/, “text”)
(replace ALL the matches)
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34. sub and gsub create new
strings.
sub! and gsub! change
the original strings
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35. Welcome to the
wonderful world of
Regular Expressions!
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