Ruby 初心者スレッド Part 37

test.rb

src = STDIN.tty? && ARGV.empty? ? DATA : ARGF
puts src.read
__END__
[contents after __END__]

$ ruby test.rb < stdin.txt
[contents of stdin.txt]
$ ruby test.rb arg.txt
[contents of arg.txt]
$ ruby test.rb
[contents after __END__]