Running JRuby on 64 bit Windows

Usually it is as simple as: download, install, run. You can run into problems however if you have both the 32 bit and 64 bit JVMs installed (which is quite often) because it will try to use the 32 bit JVM. You can check which JVM is being used from the command line:

jruby --version
jruby 1.6.3 (ruby-1.8.7-p330) (2011-07-07 965162f) (Java HotSpot(TM) 64-Bit Server VM 1.7.0) [Windows 7-amd64-java] # 64 bit
jruby 1.6.3 (ruby-1.8.7-p330) (2011-07-07 965162f) (Java HotSpot(TM) Client VM 1.6.0_26) [Windows 7-x86-java] # 32 bit

To work around this issue, specify the JVM to use in your jruby.bat (or other batch files installed by gems like vagrant.bat) explicitly. Example jruby.bat:

@ECHO OFF
java -Djruby.home=C:\jruby-1.6.3 -jar  -jar "C:\jruby-1.6.3\lib\jruby.jar" %1 %2 %3 %4 %5 %6 %7 %8 %9

Example vagrant.bat

@ECHO OFF
java -Djruby.home=C:\jruby-1.6.3 -jar "C:\jruby-1.6.3\lib\jruby.jar" "C:/jruby-1.6.3/bin/vagrant" %1 %2 %3 %4 %5 %6 %7 %8 %9