Regular Expressions

• Text pattern matching
• Used many places
  • Ruby: (1.methods.map(&:to_s).grep(/.*sp.*/))
  • Shell: (find . -regex .*st[^/]*)
  • … all over the place
• Rubular. See:
• Puzzle – Write a regex that will
  • match: pit, spot, spate, slap two, respite
  • but reject: pt, Pot, peat, part
• Puzzle – Write a single regex that matches all of these
  • <xml>
  • <opentag>
  • <closetag>
  • </closetag>
  • <with attribute=”77”>
• Regexp for a valid email address is: \b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b
  • Let’s try and test it and find flaws in it
  • And interpret it
  • Ref: All about email regex