How to extract part of a filename with Apache Ant?

Question

I want to extract the version number from a file name generated outside of my Ant script.

An external build tool (PDE build) creates a file of the form artifactid-1.2.3.201101010101.jar in a well-known directory, but I can not tell the versioning information beforehand. I need to extract the version part (1.2.3.201101010101) from that file name into an Ant property for further processing, e.g. variable substitution.

Using ant-contrib is acceptable, however I have not found a way to extract this information.

Answer 1

Here's a solution using the ant-contrib PropertyRegex task.

• Get the filename into a path.
• Convert the path to a property.
• PropertyRegex the property (ant-contrib).

You could avoid ant-contrib by writing the property value to a temporary file and then using loadfile with a filterchain to extract the artifact id from it. See this answer for an example.

  <project default="get-revision-number">
        <taskdef resource="net/sf/antcontrib/antcontrib.properties">
                <classpath>
                        <pathelement location="c:/lib/ant-contrib/ant-contrib-1.0b3.jar"/>
                </classpath>
        </taskdef>

        <target name="get-revision-number">
                <path id="artifact.id.path">
                        <fileset dir=".">
                                <include name="artifactid-*.jar"/>
                        </fileset>
                </path>
                <property name="artifact.id.file" refid="artifact.id.path"/>
                <echo message="artifact.id.file: ${artifact.id.file}"/>
                <propertyregex property="artifact.id" input="${artifact.id.file}" regexp=".*artifactid-(.*).jar" select="\1" />
                <echo message="artifact.id: ${artifact.id}"/>
        </target>
  </project>

Output

$ ant
Buildfile: C:\tmp\build.xml

get-revision-number:
     [echo] artifact.id.file: C:\tmp\artifactid-1.2.3.201101010101.jar
     [echo] artifact.id: 1.2.3.201101010101

BUILD SUCCESSFUL
Total time: 0 seconds

Answer 2

A straight solution with Ant addon Flaka :

<project name="demo" xmlns:fl="antlib:it.haefelinger.flaka">

 <property name="filename" value="artifactid-1.2.3.201101010101.jar"/>

 <!-- simple echo -->
 <fl:echo>Version => #{replace('${filename}', '$1', '.+-(.+).jar')}</fl:echo>
 <!-- create property for further processing -->
 <fl:let>fileversion := replace('${filename}', '$1', '.+-(.+).jar')</fl:let>
 <echo>$${fileversion} => ${fileversion}</echo>

</project>

output

Buildfile: /home/rosebud/workspace/ant/demo.xml
  [fl:echo] Version => 1.2.3.201101010101
     [echo] ${fileversion} => 1.2.3.201101010101
BUILD SUCCESSFUL