Note: The latest version of the script below is on github.

I work with grails quite a lot these days. I have about 5 plugins and over 10 projects that I currently work on frequently. Fairly inevitably they use an assortment of grails versions. Manually chopping and changing command lines to execute different versions gets pretty tedious.

The solution - have a grails wrapper script that detects the version of grails defined in the current project and runs the right one.

This wasn't my idea, but when I finally got fed up with manually juggling grails versions I couldn't find where I had read about it previously. So I decided to write my own version.

This relies on putting all of the grails releases that you want to support into /usr/local/grails/ using the directory names that come in the distribution file (ie grails-x.x.x). Then just create /usr/local/bin/grails with the following content:

#!/bin/bash

BASE=/usr/local/grails
APP=application.properties

VER=$1

if [ -d "$BASE/grails-$VER" ]; then
    shift
else
    if [ -f $APP ]; then
        VER=`grep app.grails.version $APP | cut -d= -f2`
        if [ ! -d "$BASE/grails-$VER" ]; then
            echo Detected version $VER could not be found
            exit 1
        fi
    else
        echo No valid version on command line and no $APP file found
        exit 1
    fi
fi

export GRAILS_HOME=$BASE/grails-$VER
$BASE/grails-$VER/bin/grails $*

In existing projects you can just run "grails" and it will pick the right version - assuming you have it installed. If you want to override the automatic choice (eg when upgrading the project) you can specify a version as the first parameter:

grails 1.3.7 upgrade

Likewise when not in a project (eg when creating a new one) you can do the same thing:

grails 1.3.5 create-app