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The groovy native launcher is a native program for launching groovy scripts. It compiles to an executable binary file, e.g. groovy.exe on Windows. Note that you still need to have groovy and a JRE or JDK installed, i.e. the native launcher is a native executable replacement for the startup scripts (groovy.bat, groovy).

The native launcher is included in the Groovy Windows installer. For other platforms, if your package management system doe not have it, you will have to compile it yourself. This is not hard, you just need to have SCons (and Python) installed.

How it works

Essentially the launcher does the same thing that the normal Java launcher (java executable) - it dynamically loads the dynamic library containing the JVM and hands the execution over to it. It does not start a separate process (i.e. it does not call the java executable).


The native launcher aims to compile and run on any os and any JDK/JRE >= 1.4. If you are using a combination of os+jdk/jre that is not supported, please post a JIRA enhancement request and support will be added.

At the moment, the following platforms have been tested:

  • Windows (XP, Vista)
  • Linux (SuSE, Ubuntu) on x86
  • Solaris on sparc
  • Mac OS X on x86

At the moment, the following JDKs/JREs have been tested

  • several versions of Sun JRE/JDK (from 1.4, 1.5 and 1.6 series)
  • JRockit (on Windows)

The current version of the native launcher works with any version of Groovy.

Pre-compiled binaries

Here are precompiled binaries for Windows:


They are not guaranteed to be completely up to date with the sources of HEAD in the Subversion repository, but they should work.

Hopefully we will have precompiled binaries for all supported platforms in the future.

What about the other Groovy executables?

The same binaries work for all the Groovy executables (groovy, groovyc, groovysh...). Just copy / (soft)link to the executable with the name of the executable you want, e.g. on Windows

copy groovy.exe groovyc.exe

and on Linux, Mac OS X, Solaris, etc.:

ln -s groovy groovyc

In addition the build produces launchers for gant and grails.

A note about gant: the gant launcher is meant for standalone gant installation. To use gant installed into your groovy installation (e.g. by groovy windows installer) use the renamed groovy executable as described above.


The source code repository for the native launcher module is at

The executables are compiled using SCons. For Windows there is a SCons installer that can be used after having installed Python - The SCons build framework is written in Python. SCons is part of Cygwin and can be installed using the usual installer. The same goes for MacPorts on Mac OS X, though there is a disk image installer as well. For Ubuntu, Debian, Fedora, SuSE, etc. SCons is packages and so the usual package management can be used to install. The build has only been tested with SCons 0.98 and greater, it may not work with earlier versions of SCons.

Once you have SCons installed then simply typing:


will compile things for the platform you are compiling on. Type:

scons -h

for a short help message about the native launcher build and

scons -H

for a message about using scons.

Setting "well known" locations at compile time 

The native launcher, if compiled with default options, will look up groovy and java installation locations as described below. However, on some platforms (linux and other *nix variants) it may be desirable for performance and security reasons to "hardwire" these locations, i.e. set them to fixed values at compile time.

Currently, native launcher supports setting three things at compile time (together or separately): GROOVY_HOME, GROOVY_STARTUP_JAR and JAVA_HOME by passing in the values to scons build via "extramacros" option.


To test that the binary you compiled uses preset locations, run groovy w/ environment variable __JLAUNCHER_DEBUG set, e.g.

The launcher will print debug info to stderr, among other things how it obtained the locations of groovy and java installations. 

Compiling on windows

On Windows you can either compile with the Microsoft cl compiler and linker or you can use GCC, either the MinGW version of the Cygwin version.

If you are not already using Cygwin, then you may want to investigate using MSYS and the MinGW toolchain.

  • Download and install Python.
    Download and install SCons.
  • Download the 'Automated MinGW Installer' from
  • Run it (it automatically installs the needed compiler, you don't have to choose additional packages)
  • Download MSYS from (don't choose a technology preview, use the executable offered as current release)
  • Run it (it install the bash and sets up the path, adding the MinGW executables to the path inherited from Windows)
  • You get an icon that starts a bash
  • Start the bash and navigate to where you downloaded the source code for the native launcher
  • Enter the command 'scons' and watch it compile the sources.

Compiling with the Cygwin or MinGW GCC produces executables that depend only dlls that are found on Windows by default. If you compile with Visual Studio, you will need an extra dll that may or may not be found on a particular windows system. The dll you need depends on the Visual Studio version, see here for details.

Try running the generated executable  - if there's no complaint about a missing dll, you're fine.


To use the native launcher, you need to either place the executable in the bin directory of groovy installation OR set the GROOVY_HOME environment variable to point to your groovy installation.

The launcher primarily tries to find the groovy installation by seeing whether it is sitting in the bin directory of one. If not, it resorts to using GROOVY_HOME environment variable. Note that this means that GROOVY_HOME environment variable does not need to be set to be able to run groovy.

Finding java installation

The native launcher uses the following order to look up java installation to use:

  1. user provided java home (using the -jh / --javahome parameter)
  2. java installation pointed to by JAVA_HOME environment variable
  3. java installation found by seeing where java executable can be found on PATH (symlinks are followed to find the actual executable)
  4. java installation marked as the current version in windows registry (value of "CurrentVersion" in keys
    • \\HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Development Kit
    • \\HKEY_LOCAL_MACHINE\SOFTWARE\JRockit\Java Development Kit
    • \\HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment
    • \\HKEY_LOCAL_MACHINE\SOFTWARE\JRockit\Java Runtime Environment
  5. hard coded "/System/Library/Frameworks/JavaVM.framework" (os-x only)

To put it another way - JAVA_HOME does not need to be set.


The native launcher accepts accepts all the same parameters as the .bat / shell script launchers, and a few others on top of that. For details, type

groovy -h

JVM parameters

Any options not recognized as options to groovy are passed on to the jvm, so you can e.g. do

groovy -Xmx250m myscript.groovy

The -client (default) and -server options to designate the type of jvm to use are also supported, so you can do

groovy -Xmx250m -server myscript.groovy

Note that no aliases like -hotspot, -jrockit etc. are accepted - it's either -client or -server

You can freely mix jvm parameters and groovy parameters. E.g. in the following -d is param to groovy and -Dmy.prop=foo / -Xmx200m are params to the jvm:

groovy -Dmy.prop=foo -d -Xmx200m myscript.groovy


The environment variable JAVA_OPTS can be used to set jvm options you want to be in effect every time you run groovy, e.g. (win example)
set JAVA_OPTS=-Xms100m -Xmx200m

You can achieve the same effect by using environment variable JAVA_TOOL_OPTIONS, see and

Note that if you set the same option from the command line that is already set in JAVA_OPTS, the one given on the command line overrides the one given in JAVA_OPTS.

Paths on Cygwin

By default, the Windows version of the native launcher only understands Windows style paths if compiled using the Microsoft compiler or the MinGW GCC. If you compile using Cygwin GCC then by default, Cygwin and Windows style paths are understood. The variable cygwinCompile controls the behaviour. If you need to exolicitly set whether the Cygwin path code is included in the build then you can set an option on the command line:

scons cygwinCompile=False

allowed values are True and False. Alternatively if you want to set the value explicitly for every build you can add a line like:

to the file in the same directory as the SConstruct file.

Cygwin path support is a little experimental, but there are no known problem at the moment. If you use it, could you please report back success or any problems via the Groovy user mailing list.

groovy.exe and groovyw.exe on Windows

Similarly to java.exe and javaw.exe on a jdk, the build process produces groovy.exe and groovyw.exe on windows. The difference is the same as w/ java.exe and javaw.exe - groovy.exe requires a console and will launch one if it is not started in a console, whereas groovyw.exe has no console (and is usually used to start apps w/ their own gui or that run on the background).

Windows file association

If you want to run your groovy scripts on windows so that they seem like any other commands (i.e. if you have myscript.groovy on your PATH, you can just type myscript), you have to associate groovy script files with the groovy executable. If you use the groovy windows installer it will do this for you. Otherwise, do as follows:

  • add .groovy to PATHEXT environment variable
  • make changes in windows registry as follows
  • run regedit.exe
  • create a new key HKEY_CLASSES_ROOT\.groovy and give it the value groovyFile
  • create HKEY_CLASSES_ROOT\groovyFile
  • under that, create HKEY_CLASSES_ROOT\groovyFile\Shell and give it value open
  • under that, create HKEY_CLASSES_ROOT\groovyFile\Shell\open\command and give it value (adjust according to your groovy location) "c:\programs\groovy-1.0\bin\groovy.exe" "%1" %*


Why have a native launcher, why aren't the startup scripts (groovy.bat, sufficient? Here are some reasons:

  • it solves an open bug : return value of groovy (on windows) is always 0 no matter what happens in the executed script ( even if you call System.exit(1) ). Granted, this could be solved by editing the launch scripts also.
  • it is slightly faster than the corresponding .bat / shell script
  • you can mix jvm params and groovy params, thus making it easier and more natural to e.g. reserve more memory for the started jvm.
  • the process will be called "groovy", not "java". Cosmetic, yes, but still nice. = )
  • fixes the problems there have been w/ the .bat launcher and paths w/ whitespace
  • on Linux, you can't use an interpreted script as a #! interpreter, because of a kernel bug

Also, the launcher has been written so that the source can be used to easily create a native launcher for any Java program.

Known issues

  • Using -server option on Solaris crashes the jvm. This is due to native library incompatibilities. A workaround is to modify LD_LIBRARY_PATH to contain the libs needed by server jvm first, e.g.

LD_LIBRARY_PATH=$JAVA_HOME/jre/lib/sparc/server:$JAVA_HOME/jre/lib/sparc:$LD_LIBRARY_PATH groovy -server myscript.groovy

Help wanted

If you have expertise with any of the following and want to help, please email me at antti dot karanta (at) hornankuusi dot fi:

  • Cygwin C API (specifically: how to successfully load and use the win <-> posix path conversion functions when loading the cygwin1.dll from a non-Cygwin C application)
  • If you are running on an OS that is not yet supported, please contact me and we'll make it work. You do not need C expertise, I'll just ask you some questions about the environment, then you compile after I've made the changes and make sure it works. Examples of environments I'd like someone who has them to help me out with: Linux on non-x86 hardware, Solaris on x86, HPUX, FreeBSD...
  • Try running on Windows 2000 or 64-bit Windows and tell me how it goes.
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