End of Life Ruby 3.1 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →

instance method

OptionParser#base

base

# File tmp/rubies/ruby-3.1.3/lib/optparse.rb, line 1251
def base
  @stack[1]
end

Subject of on_tail.

See also #banner #candidate #additional_message #def_head_option also in 4.1 · 4.0 · 3.4 · 3.3 · 3.2 · 3.0