instance method

OptionParser#warn

(?::_ToS mesg) -> void

warn(mesg = $!)

# File tmp/rubies/ruby-4.0.0/lib/optparse.rb, line 1349
def warn(mesg = $!)
  super("#{program_name}: #{mesg}")
end

Shows warning message with the program name

See also #version #ver also in 4.1 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0