Setup your .irbrc settings file to log irb sessions to ~/irb.log.

setup_irb_log.rb

log_location = File.join ENV['HOME'], 'irb.log'
irbrc = File.join ENV['HOME'], '.irbrc'
irb_logging = %[
at_exit
  open '#{log_location}', 'a' do |log|
    log << Readline::HISTORY.to_a.join("\n")
  end
end
]
 
open irbrc, 'a' do |conf|
  conf << irb_logging
end