How to determine build architecture (32bit / 64bit) with ant?

Late to the party, but what the heck...

${os.arch} only tells you if the JVM is 32/64bit. You may be running the 32bit JVM on a 64bit OS. Try this:

<var name ="os.bitness" value ="unknown"/> <if> <os family="windows"/> <then> <exec dir="." executable="cmd" outputproperty="command.ouput"> <arg line="/c SET ProgramFiles(x86)"/> </exec> <if> <contains string="${command.ouput}" substring="Program Files (x86)"/> <then> <var name ="os.bitness" value ="64"/> </then> <else> <var name ="os.bitness" value ="32"/> </else> </if> </then> <elseif> <os family="unix"/> <then> <exec dir="." executable="/bin/sh" outputproperty="command.ouput"> <arg line="/c uname -m"/> </exec> <if> <contains string="${command.ouput}" substring="_64"/> <then> <var name ="os.bitness" value ="64"/> </then> <else> <var name ="os.bitness" value ="32"/> </else> </if> </then> </elseif> </if> <echo>OS bitness: ${os.bitness}</echo> 

EDIT: As @GreenieMeanie pointed out, this requires the ant-contrib library from ant-contrib.sourceforge.net

Here is an answer that works (I tested on Kubuntu 64, Debian 32, Windows 2000 and Windows XP) without the need of external or optional ANT dependencies. It was based on @phatypus's answer.

<project name="FindArchitecture" default="check-architecture" basedir="."> <!-- Properties set: unix-like (if it is unix or linux), x64 (if it is 64-bits), register- size (32 or 64) --> <target name="check-architecture" depends="check-family,check-register" > <echo>Register size: ${register-size}</echo> <echo>OS Family: ${os-family}</echo> </target> <target name="check-family" > <condition property="os-family" value="unix" else="windows"> <os family="unix" /> </condition> <condition property="unix"> <os family="unix" /> </condition> </target> <target name="check-register" depends="reg-unix,reg-windows"> </target> <!-- Test under GNU/Linux --> <target name="reg-unix" if="unix"> <exec dir="." executable="uname" outputproperty="result"> <arg line="-m"/> </exec> <!-- String ends in 64 --> <condition property="x64"> <matches string="${result}" pattern="^.*64$"/> </condition> <condition property="register-size" value="64" else="32"> <isset property="x64"/> </condition> </target> <!-- Test under MS/Windows--> <target name="reg-windows" unless="unix"> <!-- 64 bit Windows versions have the variable "ProgramFiles(x86)" --> <exec dir="." executable="cmd" outputproperty="result"> <arg line="/c SET ProgramFiles(x86)"/> </exec> <!-- String ends in "Program Files (x86)" --> <condition property="x64"> <matches string="${result}" pattern="^.*=.*Program Files \(x86\)"/> </condition> <condition property="register-size" value="64" else="32"> <isset property="x64"/> </condition> </target> </project> 

You can just pass a parameter into the build file with the value you want. For example, if your target is dist:

ant -Dbuild.target=32 dist 

or

ant -Dbuild.target=64 dist 

and then in your Ant build script, take different actions depending on the value of the ${build.target} property (you can also use conditions to set a default value for the property if it is not set).

Or, you can check the value of the built-in system properties, such as ${os.arch}.

os.arch does not work very well, another approach is asking the JVM, for example:

 ~$ java -d32 test Mon Jun 04 07:05:00 CEST 2007 ~$ echo $? 0 ~$ java -d64 test Running a 64-bit JVM is not supported on this platform. ~$ echo $? 1 

That'd have to be in a script or a wrapper.

BTW, the os.arch (arch property of the os tag) I got for 64-bit Linux was amd64.

Assuming you are using ANT for building Java Application, Why would you need to know if it is a 32 bit arch or 64-bit? We can always pass parameters to ant tasks. A cleaner way would be to programmaticaly emit the system properties file used by Ant before calling the actual build. There is this interesting post http://forums.sun.com/thread.jspa?threadID=5306174.