facter in ant

blog/_posts/2013-02-19-using-facter-in-ant-scripts.md

@@ -0,0 +1,62 @@
+---
+title: Using Facter in Ant Scripts
+layout: post
+tags: ant facter
+description: Reusing facts from build scripts.
+---
+
+After using [puppet][1] for a while I have become use to some of the facts that [facter][2] automatically provides. When
+working with [ant][3] build scripts, I started wishing I didn't have to generate similar facts myself through various
+`exec` calls.
+
+### One Fact
+
+Instead of fragile lookups like...
+
+{% highlight xml %}
+<exec executable="/bin/bash" outputproperty="lookup.eth0">
+    <arg value="-c" />
+    <arg value="/sbin/ifconfig eth0 | grep 'inet addr' | awk -F: '{print $2}' | awk '{print $1}'" />
+</exec>
+{% endhighlight %}
+
+I can simplify it with...
+
+{% highlight xml %}
+<exec executable="/usr/bin/facter" outputproperty="lookup.eth0">
+    <arg value="ipaddress_eth0" />
+</exec>
+{% endhighlight %}
+
+
+### In Bulk
+
+Or I can load all facts with...
+
+{% highlight xml %}
+<tempfile property="tmp.facter.properties" deleteonexit="true" />
+<exec executable="/bin/bash" output="${tmp.facter.properties}" failonerror="true">
+    <arg value="-c" />
+    <arg value="/usr/bin/facter -p | /bin/sed -e 's/ => /=/'" />
+</exec>
+<property file="${tmp.facter.properties}" prefix="facter" />
+{% endhighlight %}
+
+And reference a fact in my task...
+
+{% highlight xml %}
+<exec executable="${basedir}/bin/configure-env">
+    <arg value="--set-listen" />
+    <arg value="${facter.ipaddress_eth0}" />
+</exec>
+{% endhighlight %}
+
+### Summary
+
+So now it's much easier to reference environment information from property files (via interpolation), make targets more
+conditional, and, of course, from actual tasks.
+
+
+ [1]: https://puppetlabs.com/puppet/what-is-puppet/
+ [2]: https://puppetlabs.com/puppet/related-projects/facter/
+ [3]: http://ant.apache.org/