How to find a hint about a method and its parameters from the command line?

Question

Ruby on Rails

I am a newbie developer in ruby ​​on rails. And it would help me a lot if I could get a hint about the parameters of a method (eg File.open) from the command line. For example help File.open.

Answer 1

Ruby Ri Tool

Answer 2

Replace default irb with pry

gem install pry
gem install pry-doc (если нужна стандартая либа)
pry

Now a lot of useful commands are available to you (the whole list is available through help), for example:
"ls File" - list of all methods for the File class
object "$ File.open" - source code of the method
"? File.open" - docks to this method

Answer 3

irb

--help
Array#sort
Array.new
File.open