backticks work very well as well and are in the bourne scripting
metaphor. Interpolation (i.e. #{self} will also work inside ruby's
back ticks.

They will return string. to be used within the program. pipes and
redirection can be used inside as so:

ps = "$2"
pid =  `ps aux | awk '{print #{ps}}'`
printf pid

$$ gives you the ruby programs process id
$0 returns a string of the program that is running
$* will give you arg list

here = <<FILE
  will work as
  well which also
  include #{interpolation}
FILE

Others can be found in a file called English.rb

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