Regular Expressions

You should not be permitted to write production code if you do not have an journeyman licence in regular expressions or floating point math. —Rob Pike

#+begin_src sh . single character \ escape ? optional character

zero or more of previous#

• one ore more

[] or for specific characters ^ not \d digit \s whitespace (tabs, carriage returns, null) \b word boundary \d{4} equiv \d\d\d\d parenthesis and ? makes the stuff in parens optional same for + and * \w{n} n letter words \w{n,k} n or k letter words #+end_src

?*+ are “quantifiers”

*+ are greedy

*? is the non-greedy version

try not to use ranges: [0-9].