$ mkdir /tmp/classpath_seek
$ cd !$
$ rvm use jruby-9.0.1.0
$ touch foo.rb
$ irb
>> $CLASSPATH <<  Dir.pwd
=> ["file:/Users/me/.m2/repository/jline/jline/2.11/jline-2.11.jar", "file:/Users/me/.rvm/rubies/jruby-9.0.1.0/lib/ruby/stdlib/readline.jar", "file:/private/tmp/classpath_seek/"]
>> f = File.open('classpath:foo.rb')
=> #<File:classpath:foo.rb>
>> f.seek(0)
Errno::EPIPE: Broken pipe - classpath:foo.rb
    from org/jruby/RubyIO.java:1649:in `seek'
    from (irb):4:in `<eval>'
    from org/jruby/RubyKernel.java:978:in `eval'
    from org/jruby/RubyKernel.java:1291:in `loop'
    from org/jruby/RubyKernel.java:1098:in `catch'
    from org/jruby/RubyKernel.java:1098:in `catch'
    from /Users/me/.rvm/rubies/jruby-9.0.1.0/bin/irb:13:in `<top>'

>> f = File.open(File.join(Dir.pwd, 'foo.rb'))
=> #<File:/private/tmp/classpath_seek/foo.rb>
>> f.seek(0)
=> 0