Question

Out of the following the last one does not work:

puts node.elasticsearch[:plugin][:jetty][:name]
puts node.elasticsearch[:plugin]['jetty'][:name]
puts node.elasticsearch[:plugin]["'#{entry}'"][:name]

What syntax do I need to follow in order to use a variable’s value in the index when accessing a multi dimensional array?

UPDATE:
I think entry is a String but I could be wrong so here’s the statement that sets it up for you the educated helper to determine what’s what:

Dir.entries("/var/plugins/").any? do |entry|
    puts node.elasticsearch[:plugin][:jetty][:name]
    puts node.elasticsearch[:plugin]['jetty'][:name]
    puts node.elasticsearch[:plugin]["'#{entry}'"][:name]
end

Answer 1

Your hash is indexed with symbols, so you should convert your string into a symbol, with entry.intern().

puts node.elasticsearch[:plugin][entry.intern][:name]

Edit: to_sym and intern are aliases of the String class. So entry has to be a string, which it seems to be according to your attempts.