This short tutorial shows how to get an exit code from Ant and act upon it. This can be useful when building a massive application that requires several Ant scripts/targets and a collection of shell scripts.

The rule of thumb when building the system is “when it should fail -> it should fail”. Sounds weird, but it is really true.

If the whole build of the application takes 15-20 minutes, and one of the libraries failed to build (for example), the whole build should fail. Otherwise, if the build master inspects the logs, and sees something went wrong (in case it is logged), s/he would have to spend another 20 minutes to rebuild it. Or what is even worse, the application could end up in an inconsistent state, without anybody raising a flag, and that would be very dangerous, especially if the current release goes beyond integration builds, for example to quality assurance or even worse – to production.

So, above are the reasons, below is an ultra simple example with a solution:

Let’s say we have an Ant script (build.xml) that checks for duplicate jars in a directory. The target name that does that is “check-duplicate-jars”:

build.xml:

    <target name="check-duplicate-jars" depends="some-other-task">
        <!-- does its magic here -->
    </target>

Let’s say we also have a simple shell script that calls “ant “. If this shell script is in the same directory as the “build.xml”, we can call it like this “./callant.sh check-duplicate-jars”, and it should check if there are any duplicate jars. Let’s run the shell script:

[user@host]$ ./callant.sh check-duplicate-jars
ANT: Running check-duplicate-jars task...
Buildfile: build.xml
 
check-duplicate-jars:
     [echo] Checking for duplicate jars......
     [exec] ***********    NO DUPLICATE JARS FOUND IN LIB!    ***********
 
BUILD SUCCESSFUL
Total time: 3 seconds
ANT: Return code is: "0"
GREAT SUCCESS: Niiice - I liiike!

This is an expected behavior. However what would be nice is to have this shell script “fail hard”, in case the Ant script (build.xml) fails.

Let’s try to misspell the target name “check-duplicate-jar” (should be plural: “check-duplicate-jars”) and run it:

[user@host]$ ./call-ant.sh check-duplicate-jar
ANT: Running check-duplicate-jar task...
Buildfile: build.xml
 
BUILD FAILED
Target `check-duplicate-jar' does not exist in this project.
 
Total time: 1 second
ANT: Return code is: "1"
BUILD ERROR: I am failing hard...

Wonderful – it failed! That is an expected behavior. And here is a sneak peek to the magic box – the “callant.sh” shell script:

#!/bin/bash
 
tname=$1
 
echo "ANT: Running $tname task..."
ant $tname
 
antReturnCode=$?
 
echo "ANT: Return code is: \""$antReturnCode"\""
 
if [ $antReturnCode -ne 0 ];then
 
    echo "BUILD ERROR: I am failing hard..."
    exit 1;
else
 
    echo "GREAT SUCCESS: Niiice - I liiike!"
    exit 0;
fi

Hence the whole magic is here:

antReturnCode=$?

In general, “$?” will return an exist code of any executable run within the shell script.
Well, now you ready for the massive build process. Get to work, and may the build force be with you! :)

This entry was posted on Friday, October 24th, 2008 at 13:59 and is filed under ant, howto, shell, tutorials. You can follow any comments to this entry through the RSS 2.0 feed. You can leave a comment, or trackback from your own site.