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Ant task to run an Ant target only if a file exists?

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How do I run a specific target in Ant?

To run the ant build file, open up command prompt and navigate to the folder, where the build. xml resides, and then type ant info. You could also type ant instead. Both will work,because info is the default target in the build file.

What is Basedir in Ant?

The 'basedir' is the base directory from which any relative directories used within the Ant build file are referenced from. If this is omitted the parent directory of the build file will be used.

What is Replace task in Ant?

Replace is a directory based task for replacing the occurrence of a given string with another string in selected file. If you want to replace a text that crosses line boundaries, you must use a nested <replacetoken> element. The output file is only written if it differs from the existing file.

What is the default target in Ant?

the default target to use when no target is supplied. No; however, since Ant 1.6. 0, every project includes an implicit target that contains any and all top-level tasks and/or types. This target will always be executed as part of the project's initialization, even when Ant is run with the -projecthelp option.


Available and Condition

<target name="check-abc">
    <available file="abc.txt" property="abc.present"/>
</target>

<target name="do-if-abc" depends="check-abc" if="abc.present">
    ...
</target> 

This might make a little more sense from a coding perspective (available with ant-contrib: http://ant-contrib.sourceforge.net/):

<target name="someTarget">
    <if>
        <available file="abc.txt"/>
        <then>
            ...
        </then>
        <else>
            ...
        </else>
    </if>
</target>

Since Ant 1.8.0 there's apparently also resourceexists

From http://ant.apache.org/manual/Tasks/conditions.html

Tests a resource for existance. since Ant 1.8.0

The actual resource to test is specified as a nested element.

An example:

<resourceexists>
  <file file="${file}"/>
</resourceexists>

I was about rework the example from the above good answer to this question, and then I found this

As of Ant 1.8.0, you may instead use property expansion; a value of true (or on or yes) will enable the item, while false (or off or no) will disable it. Other values are still assumed to be property names and so the item is enabled only if the named property is defined.

Compared to the older style, this gives you additional flexibility, because you can override the condition from the command line or parent scripts:

<target name="-check-use-file" unless="file.exists">
    <available property="file.exists" file="some-file"/>
</target>
<target name="use-file" depends="-check-use-file" if="${file.exists}">
    <!-- do something requiring that file... -->
</target>
<target name="lots-of-stuff" depends="use-file,other-unconditional-stuff"/>

from the ant manual at http://ant.apache.org/manual/properties.html#if+unless

Hopefully this example is of use to some. They're not using resourceexists, but presumably you could?.....


I think its worth referencing this similar answer: https://stackoverflow.com/a/5288804/64313

Here is a another quick solution. There are other variations possible on this using the <available> tag:

# exit with failure if no files are found
<property name="file" value="${some.path}/some.txt" />
<fail message="FILE NOT FOUND: ${file}">
    <condition><not>
        <available file="${file}" />
    </not></condition>
</fail>