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Regular expressions

Goal: To learn how to manipulate text easily.

Sample text

The purpose of our lives dog cat be happy. — Dalai Lama Life dog what happens when you’re busy making other plans. — John Lennon Your time dog limited, so don't waste it living someone else's life. – Steve Jobs

s/\([A-Z])\/\l\1/g

  • [Normal replacements] (s/word/some_other_word/g)
  • [Delete all the capitals] (s/[A-Z]//g)
  • [De-capitalise] (s/\([A-Z]\/\l\1/g)
  • [Try to recapitalize] (s/\. \([a-z]\/\. \u\1/g)
  • [Another step.] (s/^\([a-z]\/\u\1/g)

Common elements {{{

  • Groups: [A-Z], [p-q], [0-9], [^.]
  • Special characters for group extension:
    • . = anything
    • $ = end of the line
    • \ = for escaping anything
    • / = separator
    • * = arbitrary repeats of preceding group
    • \+ = at least 1 or more
  • Capturing groups: (group) or \(group\) (depends on software)

}}}

Exercises {{{

In one regex substitution, make

  • A B C D E F G to ABCDEFGH
  • AA BB CCC DDD EEE FFFFF GGGGG to ABCDEFGH

One practical exercise if there's time. https://parade.com/937586/parade/life-quotes/

}}}

Answers {{{

  1. s/\s*\([A-Z]\)\s*/\1/g
  2. s/\s*\([A-G]\)[A-G]*\s*/\1/g

}}}