How to pull out a substring in Ant

Question

Is there a way to pull a substring from an Ant property and place that substring into it's own property?

Can you be more specific about what you're trying to do? Why wouldn't it make more sense to define a property to hold the value you're depending on and use it in multiple places? If your Ant properties are changing often enough that you need to programatically react to them, you may be doing something else wrong. — PanCrit, Jun 03 '09 at 16:42

score 39 · Accepted Answer · edited Aug 16 '11 at 20:31

I use scriptdef to create a javascript tag to substring, for exemple:

 <project>
  <scriptdef name="substring" language="javascript">
     <attribute name="text" />
     <attribute name="start" />
     <attribute name="end" />
     <attribute name="property" />
     <![CDATA[
       var text = attributes.get("text");
       var start = attributes.get("start");
       var end = attributes.get("end") || text.length();
       project.setProperty(attributes.get("property"), text.substring(start, end));
     ]]>
  </scriptdef>
  ........
  <target ...>
     <substring text="asdfasdfasdf" start="2" end="10" property="subtext" />
     <echo message="subtext = ${subtext}" />
  </target>
 </project>

score 23 · Answer 2 · edited Apr 11 '18 at 12:41

23

You could try using PropertyRegex from Ant-Contrib.

   <propertyregex property="destinationProperty"
              input="${sourceProperty}"
              regexp="regexToMatchSubstring"
              select="\1"
              casesensitive="false" />

edited Apr 11 '18 at 12:41

Peter Lang

54,264
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answered Jun 03 '09 at 19:06

Instantsoup

14,825
5
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Additional note: In case this is done dynamically in a loop, use `override="true"` to override any previous value. – robinst Oct 09 '13 at 15:08

score 10 · Answer 3 · answered Feb 09 '12 at 08:33

Since I prefer to use vanilla Ant, I use a temporary file. Works everywhere and you can leverage replaceregex to get rid of the part of the string you don't want. Example for munging Git messages:

    <exec executable="git" output="${git.describe.file}" errorproperty="git.error" failonerror="true">
        <arg value="describe"/>
        <arg value="--tags" />
        <arg value="--abbrev=0" />
    </exec>
    <loadfile srcfile="${git.describe.file}" property="git.workspace.specification.version">
        <filterchain>
           <headfilter lines="1" skip="0"/>
           <tokenfilter>
              <replaceregex pattern="\.[0-9]+$" replace="" flags="gi"/>
           </tokenfilter>
           <striplinebreaks/>
        </filterchain>
    </loadfile>

If you're dealing with a property to start with, you can eschew the file by doing something like ${property.here} — Scott, Jul 02 '13 at 15:49

score 7 · Answer 4 · answered Dec 11 '19 at 12:41

7

I guess an easy vanilla way to do this is:

<loadresource property="destinationProperty">
    <concat>${sourceProperty}</concat>
    <filterchain>
        <replaceregex pattern="regexToMatchSubstring" replace="\1" />
    </filterchain>
</loadresource>

answered Dec 11 '19 at 12:41

Markus Rohlof

380
3
13

score 2 · Answer 5 · answered Jun 03 '09 at 18:53

I would go with the brute force and write a custom Ant task:

public class SubstringTask extends Task {

    public void execute() throws BuildException {
        String input = getProject().getProperty("oldproperty");
        String output = process(input);
        getProject().setProperty("newproperty", output);
    }
}

What's left it to implement the String process(String) and add a couple of setters (e.g. for the oldproperty and newproperty values)

Rebse · Answer 6 · 2011-06-14T21:02:23.953

0

i would use script task for that purpose, i prefer ruby, example cut off the first 3 chars =

<project>
  <property name="mystring" value="foobarfoobaz"/>  
   <target name="main"> 
    <script language="ruby">
     $project.setProperty 'mystring', $mystring[3..-1]
    </script>
    <echo>$${mystring} == ${mystring}</echo>
   </target>    
  </project>

output =

main:
     [echo] ${mystring} == barfoobaz

using the ant api with method project.setProperty() on an existing property will overwrite it, that way you can work around standard ant behaviour, means properties once set are immutable

edited Jun 14 '11 at 21:02

answered Sep 04 '09 at 20:37

Rebse

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Hi, i got this error: Unable to create javax script engine for ruby – Jarod Law Ding Yong Aug 09 '11 at 09:02
Jarod, you need bsf.jar (http://jakarta.apache.org/bsf) and jruby.jar (http://www.jruby.org), see also http://ant.apache.org/manual/install.html#librarydependencies, note that the link to jruby is wrong on that page. – Rebse Aug 14 '11 at 18:05

How to pull out a substring in Ant

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