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main_block.rb

This Ruby code snippet demonstrates a common idiom to ensure a block of code only runs when the Ruby file is executed directly (as a script), and not when it’s required as a library in another file. __FILE__ holds the path to the current file, and $0 holds the name of the script being executed. The if condition checks if these are equal, meaning the file is the main program being run. The => nil indicates the script doesn’t explicitly return a value; implicitly it returns nil.

Ruby code snippet

if __FILE__ == $0
  # Code block to be executed only if the script is run directly

  # Add your script's main logic here
end
#=> nil

Executed with Ruby 3.4.5.