All commands in irb giving "NoMethodError: undefined method `write' for nil:NilClass"

Question

I am trying to get the current ruby version from IRB but its giving me this error:

>> RUBY_VERSION
NoMethodError: undefined method `write' for nil:NilClass
    from /usr/local/lib/ruby/1.9.1/irb.rb:311:in `printf'
    from /usr/local/lib/ruby/1.9.1/irb.rb:311:in `output_value'
    from /usr/local/lib/ruby/1.9.1/irb.rb:160:in `block (2 levels) in eval_input'
    from /usr/local/lib/ruby/1.9.1/irb.rb:273:in `signal_status'
    from /usr/local/lib/ruby/1.9.1/irb.rb:156:in `block in eval_input'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:243:in `block (2 levels) in each_top_level_statement'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:229:in `loop'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:229:in `block in each_top_level_statement'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:228:in `catch'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:228:in `each_top_level_statement'
    from /usr/local/lib/ruby/1.9.1/irb.rb:155:in `eval_input'
    from /usr/local/lib/ruby/1.9.1/irb/ext/multi-irb.rb:166:in `block (2 levels) in irb'
    from /usr/local/lib/ruby/1.9.1/irb/ext/multi-irb.rb:165:in `catch'
    from /usr/local/lib/ruby/1.9.1/irb/ext/multi-irb.rb:165:in `block in irb'
Maybe IRB bug!

ruby -v shows ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin11.2.0]

I am using Mac OS X Lion

UPDATE: Actually, it doesn't run anything at all.

>> a = 'Hello, World!'
NoMethodError: undefined method `write' for nil:NilClass
    from /usr/local/lib/ruby/1.9.1/irb.rb:311:in `printf'
    from /usr/local/lib/ruby/1.9.1/irb.rb:311:in `output_value'
    from /usr/local/lib/ruby/1.9.1/irb.rb:160:in `block (2 levels) in eval_input'
    from /usr/local/lib/ruby/1.9.1/irb.rb:273:in `signal_status'
    from /usr/local/lib/ruby/1.9.1/irb.rb:156:in `block in eval_input'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:243:in `block (2 levels) in each_top_level_statement'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:229:in `loop'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:229:in `block in each_top_level_statement'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:228:in `catch'
    from /usr/local/lib/ruby/1.9.1/irb/ruby-lex.rb:228:in `each_top_level_statement'
    from /usr/local/lib/ruby/1.9.1/irb.rb:155:in `eval_input'
    from /usr/local/lib/ruby/1.9.1/irb/ext/multi-irb.rb:166:in `block (2 levels) in irb'
    from /usr/local/lib/ruby/1.9.1/irb/ext/multi-irb.rb:165:in `catch'
    from /usr/local/lib/ruby/1.9.1/irb/ext/multi-irb.rb:165:in `block in irb'
Maybe IRB bug!

UPDATE # 2: (For the Tin Man) Using /usr/bin/irb, I get

>> 5+5
NoMethodError: undefined method `write' for nil:NilClass
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:310:in `printf'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:310:in `output_value'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:159:in `eval_input'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:271:in `signal_status'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:155:in `eval_input'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/ruby-lex.rb:244:in `each_top_level_statement'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/ruby-lex.rb:230:in `loop'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/ruby-lex.rb:230:in `each_top_level_statement'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/ruby-lex.rb:229:in `catch'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/ruby-lex.rb:229:in `each_top_level_statement'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:154:in `eval_input'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:71:in `start'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:70:in `catch'
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb.rb:70:in `start'
    from /usr/bin/irb:13
Maybe IRB bug!!

Answer 1

Try /usr/bin/irb to get to Apple's installation of Ruby.

Installing Ruby on Lion using instructions for Leopard isn't a good idea. You have to remember that languages and OS details change.

The information at "Building Ruby 1.9.3 on Lion with Xcode 4.2 using ./configure --with-gcc=clang" should help. Also "Error installing 1.9.3 with RVM on Lion" has useful information about XCode.