Apache Ant Script to Reset and Increment Build Numbers (CI-Friendly Modes)

Originally published on 2009-06-20; fully revised and updated.

This guide shows how to manage a resettable, multi-part build number in Apache Ant. It is useful for teams maintaining Ant-based CI/release pipelines and needing predictable version increments for major, minor, hotfix, revision, and optional continuous builds.

Source context: original DevOpsSchool post.

How this build numbering pattern works

The script keeps version state in a build.number file and updates it based on -Dincrement=.... By default, the build number is four parts (major.minor.hotfix.revision). For continuous builds, it can include a fifth part (continuous).

Create the build.number state file

Initialize the property file once in your project root:

major.number=1
minor.number=0
hotfix.number=0
revision.number=0
continuous.number=0

Add task definitions and targets in build.xml

The original snippet relies on Ant-Contrib tasks (such as var, switch, math, if) plus an unset task from Antelope.

Task definitions

<taskdef resource="net/sf/antcontrib/antlib.xml"/>
<taskdef name="unset" classname="ise.antelope.tasks.Unset"/>Code language: HTML, XML (xml)

Target 1: initialize counters from build.number

<target name="initBuildNum" description="Get current build number properties">
    <property file="build.number"/>
    <var name="next.major" value="${major.number}"/>
    <var name="next.minor" value="${minor.number}"/>
    <var name="next.hotfix" value="${hotfix.number}"/>
    <var name="next.revision" value="${revision.number}"/>
    <var name="next.continuous" value="${continuous.number}"/>
</target>Code language: HTML, XML (xml)

Target 2: apply increment logic

<target name="getBuildNum">
    <switch value="${increment}">
        <case value="rebuild"/>

        <case value="major">
            <math result="next.major" operand1="${next.major}" operation="+" operand2="1" datatype="int"/>
            <var name="next.minor" value="1"/>
            <var name="next.hotfix" value="0"/>
            <var name="next.revision" value="1"/>
        </case>

        <case value="minor">
            <math result="next.minor" operand1="${next.minor}" operation="+" operand2="1" datatype="int"/>
            <var name="next.hotfix" value="0"/>
            <var name="next.revision" value="1"/>
        </case>

        <case value="hotfix">
            <math result="next.hotfix" operand1="${next.hotfix}" operation="+" operand2="1" datatype="int"/>
            <var name="next.revision" value="1"/>
        </case>

        <case value="continuous">
            <math result="next.continuous" operand1="${next.continuous}" operation="+" operand2="1" datatype="int"/>
        </case>

        <case value="contReset">
            <var name="next.continuous" value="1"/>
        </case>

        <default>
            <math result="next.revision" operand1="${next.revision}" operation="+" operand2="1" datatype="int"/>
        </default>
    </switch>
</target>Code language: HTML, XML (xml)

Target 3: persist and expose full.buildnumber

<target name="setBuildNumber" depends="initBuildNum,getBuildNum">
    <propertyfile file="build.number">
        <entry key="major.number" value="${next.major}"/>
        <entry key="minor.number" value="${next.minor}"/>
        <entry key="hotfix.number" value="${next.hotfix}"/>
        <entry key="revision.number" value="${next.revision}"/>
        <entry key="continuous.number" value="${next.continuous}"/>
    </propertyfile>

    <unset name="major.number"/>
    <unset name="minor.number"/>
    <unset name="hotfix.number"/>
    <unset name="revision.number"/>
    <unset name="continuous.number"/>

    <property file="build.number"/>

    <if>
        <or>
            <equals arg1="${increment}" arg2="continuous"/>
            <equals arg1="${increment}" arg2="contReset"/>
        </or>
        <then>
            <property name="full.buildnumber" value="${major.number}.${minor.number}.${hotfix.number}.${revision.number}.${continuous.number}"/>
        </then>
        <else>
            <property name="full.buildnumber" value="${major.number}.${minor.number}.${hotfix.number}.${revision.number}"/>
        </else>
    </if>

    <echo>${full.buildnumber}</echo>
</target>Code language: HTML, XML (xml)

Make your main build target depend on setBuildNumber so the version is calculated before packaging.

<target name="build" depends="setBuildNumber,compile,test,package"/>Code language: HTML, XML (xml)

Command examples

ant
ant -Dincrement=major
ant -Dincrement=minor
ant -Dincrement=hotfix
ant -Dincrement=continuous
ant -Dincrement=contReset

Build number update workflow

flowchart TD
    A[Run ant with optional increment] --> B[Load build.number]
    B --> C[Evaluate increment mode]
    C --> D[Update counters in memory]
    D --> E[Write counters to build.number]
    E --> F[Reload properties]
    F --> G[Set full.buildnumber]
    G --> H[Echo version for downstream targets]

Common pitfalls and best practices

• Keep build.number under controlled write access; concurrent CI jobs can overwrite each other.
• Ensure required task libraries are on Ant’s classpath before running this script.
• Document when to use major, minor, and hotfix to avoid accidental version jumps.
• Be explicit in CI: pass -Dincrement=... rather than relying on defaults.
• If you need immutable build metadata, publish ${full.buildnumber} as an artifact variable after each run.

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

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