Selectors

Selectors are a mechanism whereby the files that make up a <fileset> can be selected based on criteria other than filename as provided by the <include> and <exclude> tags.

How to use a Selector

A selector is an element of FileSet, and appears within it. It can also be defined outside of any target by using the <selector> tag and then using it as a reference.

Different selectors have different attributes. Some selectors can contain other selectors, and these are called Selector Containers. There is also a category of selectors that allow user-defined extensions, called Custom Selectors. The ones built in to Apache Ant are called Core Selectors.

Core Selectors

Core selectors are the ones that come standard with Ant. They can be used within a fileset and can be contained within Selector Containers.

The core selectors are:

• <contains>—Select files that contain a particular text string
• <date>—Select files that have been modified either before or after a particular date and time
• <depend>—Select files that have been modified more recently than equivalent files elsewhere
• <depth>—Select files that appear so many directories down in a directory tree
• <different>—Select files that are different from those elsewhere
• <filename>—Select files whose name matches a particular pattern. Equivalent to the include and exclude elements of a patternset.
• <present>—Select files that either do or do not exist in some other location
• <containsregexp>—Select files that match a regular expression
• <size>—Select files that are larger or smaller than a particular number of bytes.
• <type>—Select files that are either regular files or directories.
• <modified>—Select files if the return value of the configured algorithm is different from that stored in a cache.
• <signedselector>—Select files if they are signed, and optionally if they have a signature of a certain name.
• <scriptselector>—Use a BSF or JSR 223 scripting language to create your own selector
• <readable>—Select files if they are readable.
• <writable>—Select files if they are writable.
• <executable>—Select files if they are executable.
• <symlink>—Select files if they are symlinks.
• <ownedBy>—Select files if they are owned by a given user.
• <posixGroup>—Select files if they have a given POSIX group.
• <posixPermissions>—Select files if they have given POSIX permissions.

Contains Selector

The <contains> tag in a FileSet limits the files defined by that fileset to only those which contain the string specified by the text attribute.

The <contains> selector can be used as a ResourceSelector (see the <restrict> ResourceCollection).

Here is an example of how to use the Contains Selector:

<fileset dir="${doc.path}" includes="**/*.html">
    <contains text="script" casesensitive="no"/>
</fileset>

Selects all the HTML files that contain the string script.

Date Selector

The <date> tag in a FileSet will put a limit on the files specified by the include tag, so that tags whose last modified date does not meet the date limits specified by the selector will not end up being selected.

Here is an example of how to use the Date Selector:

<fileset dir="${jar.path}" includes="**/*.jar">
    <date datetime="01/01/2001 12:00 AM" when="before"/>
</fileset>

Selects all JAR files which were last modified before midnight January 1, 2001.

Depend Selector

The <depend> tag selects files whose last modified date is later than another, equivalent file in another location.

The <depend> tag supports the use of a contained <mapper> element to define the location of the file to be compared against. If no <mapper> element is specified, the identity type mapper is used.

The <depend> selector is case-sensitive.

Here is an example of how to use the Depend Selector:

<fileset dir="${ant.1.5}/src/main" includes="**/*.java">
    <depend targetdir="${ant.1.4.1}/src/main"/>
</fileset>

Selects all the Java source files which were modified in the 1.5 release.

Depth Selector

The <depth> tag selects files based on how many directory levels deep they are in relation to the base directory of the fileset.

Here is an example of how to use the Depth Selector:

<fileset dir="${doc.path}" includes="**/*">
    <depth max="1"/>
</fileset>

Selects all files in the base directory and one directory below that.

Different Selector

The <different> selector will select a file if it is deemed to be 'different' from an equivalent file in another location. The rules for determining difference between the two files are as follows:

1. If a file is only present in the resource collection you apply the selector to but not in targetdir (or after applying the mapper) the file is selected.
2. If a file is only present in targetdir (or after applying the mapper) it is ignored.
3. Files with different lengths are different.
4. If ignoreFileTimes is turned off, then differing file timestamps will cause files to be regarded as different.
5. Unless ignoreContents is set to true, a byte-for-byte check is run against the two files.

This is a useful selector to work with programs and tasks that don't handle dependency checking properly; even if a predecessor task always creates its output files, followup tasks can be driven off copies made with a different selector, so their dependencies are driven on the absolute state of the files, not just a timestamp. For example: anything fetched from a web site, or the output of some program. To reduce the amount of checking, when using this task inside a <copy> task, set preservelastmodified to true to propagate the timestamp from the source file to the destination file.

The <different> selector supports the use of a contained <mapper> element to define the location of the file to be compared against. If no <mapper> element is specified, the identity type mapper is used.

Here is an example of how to use the Different Selector:

<fileset dir="${ant.1.5}/src/main" includes="**/*.java">
    <different targetdir="${ant.1.4.1}/src/main"
        ignoreFileTimes="true"/>
</fileset>

Compares all the Java source files between the 1.4.1 and the 1.5 release and selects those who are different, disregarding file times.

Filename Selector

The <filename> tag acts like the <include> and <exclude> tags within a fileset. By using a selector instead, however, one can combine it with all the other selectors using whatever selector container is desired.

The <filename> selector is case-sensitive.

Here is an example of how to use the Filename Selector:

<fileset dir="${doc.path}" includes="**/*">
    <filename name="**/*.css"/>
</fileset>

Selects all the cascading style sheet files.

Present Selector

The <present> tag selects files that have an equivalent file in another directory tree.

The <present> tag supports the use of a contained <mapper> element to define the location of the file to be tested against. If no <mapper> element is specified, the identity type mapper is used.

The <present> selector is case-sensitive.

Here is an example of how to use the Present Selector:

<fileset dir="${ant.1.5}/src/main" includes="**/*.java">
    <present present="srconly" targetdir="${ant.1.4.1}/src/main"/>
</fileset>

Selects all the Java source files which are new in the 1.5 release.

Regular Expression Selector

The <containsregexp> tag in a FileSet limits the files defined by that fileset to only those which contents contain a match to the regular expression specified by the expression attribute.

The <containsregexp> selector can be used as a ResourceSelector (see the <restrict> ResourceCollection).

Here is an example of how to use the regular expression Selector:

<fileset dir="${doc.path}" includes="*.txt">
    <containsregexp expression="[4-6]\.[0-9]"/>
</fileset>

Selects all the text files that match the regular expression (have a 4, 5 or 6 followed by a period and a number from 0 to 9).

Size Selector

The <size> tag in a FileSet will put a limit on the files specified by the include tag, so that tags which do not meet the size limits specified by the selector will not end up being selected.

Here is an example of how to use the Size Selector:

<fileset dir="${jar.path}">
  <patternset>
    <include name="**/*.jar"/>
  </patternset>
  <size value="4" units="Ki" when="more"/>
</fileset>

Selects all JAR files that are larger than 4096 bytes.

Type Selector

The <type> tag selects files of a certain type: directory or regular.

Here is an example of how to use the Type Selector to select only directories in ${src}

<fileset dir="${src}">
  <type type="dir"/>
</fileset>

The Type Selector is often used in conjunction with other selectors. For example, to select files that also exist in a template directory, but avoid selecting empty directories, use:

<fileset dir="${src}">
    <and>
        <present targetdir="template"/>
        <type type="file"/>
    </and>
</fileset>

Modified Selector

The <modified> selector computes a value for a file, compares that to the value stored in a cache and select the file, if these two values differ.

Because this selector is highly configurable the order in which the selection is done is:

1. get the absolute path for the file
2. get the cached value from the configured cache (absolute path as key)
3. get the new value from the configured algorithm
4. compare these two values with the configured comparator
5. update the cache if needed and requested
6. do the selection according to the comparison result

The comparison, computing of the hashvalue and the store is done by implementation of special interfaces. Therefore they may provide additional parameters.

The <modified> selector can be used as a ResourceSelector (see the <restrict> ResourceCollection). In that case it maps simple file resources to files and does its job. If the resource is from another type, the <modified> selector tries to (attention!) copy the content into a local file for computing the hashvalue.

If the source resource is not a filesystem resource the modified selector will download it to the temporary directory.

Parameters specified as nested elements

The <modified> selector supports a nested <classpath> element that represents a path-like structure for finding custom interface implementations.

All attributes of a <modified> selector can be set with nested <param/> tags. Additional values can be set with <param/> tags according to the rules below.

algorithm

Same as algorithm attribute, with the following additional values:

cache

Same as cache attribute, with the following additional values:

comparator

Same as comparator attribute.

algorithmclass

Same as algorithmclass attribute.

comparatorclass

Same as comparatorclass attribute.

cacheclass

Same as cacheclass attribute.

update

Same as update attribute.

seldirs

Same as comparatorclass attribute.

Examples

Here are some examples of how to use the Modified Selector:

<copy todir="dest">
    <fileset dir="src">
        <modified/>
    </fileset>
</copy>

This will copy all files from src to dest which content has changed. Using an updating PropertyfileCache with cache.properties and MD5-DigestAlgorithm.

<copy todir="dest">
    <fileset dir="src">
        <modified update="true"
                  seldirs="true"
                  cache="propertyfile"
                  algorithm="digest"
                  comparator="equal">
            <param name="cache.cachefile"     value="cache.properties"/>
            <param name="algorithm.algorithm" value="MD5"/>
        </modified>
    </fileset>
</copy>

This is the same example rewritten as CoreSelector with setting the all the values (same as defaults are).

<copy todir="dest">
    <fileset dir="src">
        <custom class="org.apache.tools.ant.types.selectors.modifiedselector.ModifiedSelector">
            <param name="update"     value="true"/>
            <param name="seldirs"    value="true"/>
            <param name="cache"      value="propertyfile"/>
            <param name="algorithm"  value="digest"/>
            <param name="comparator" value="equal"/>
            <param name="cache.cachefile"     value="cache.properties"/>
            <param name="algorithm.algorithm" value="MD5"/>
        </custom>
    </fileset>
</copy>

And this is the same rewritten as CustomSelector.

<target name="generate-and-upload-site">
    <echo> generate the site using forrest </echo>
    <antcall target="site"/>

    <echo> upload the changed file </echo>
    <ftp server="${ftp.server}" userid="${ftp.user}" password="${ftp.pwd}">
        <fileset dir="htdocs/manual">
            <modified/>
        </fileset>
    </ftp>
</target>

A useful scenario for this selector inside a build environment for homepage generation (e.g. with Apache Forrest). Here all changed files are uploaded to the server. The CacheSelector saves therefore much upload time.

<modified cacheclassname="com.mycompany.MyCache">
    <classpath>
        <pathelement location="lib/mycompany-antutil.jar"/>
    </classpath>
</modified>

Uses com.mycompany.MyCache from a jar outside of Ant's own classpath as cache implementation

Note on RuleBasedCollator

The RuleBasedCollator needs a format for its work, but its needed while instantiating. There is a problem in the initialization algorithm for this case. Therefore you should not use this (or tell me the workaround :-).

Signed Selector

The <signedselector> tag selects signed files and optionally signed with a certain name.

Since Apache Ant 1.7

Readable Selector

The <readable> selector selects only files that are readable. Ant only invokes java.io.File#canRead so if a file is unreadable but JVM cannot detect this state, this selector will still select the file.

Writable Selector

The <writable> selector selects only files that are writable. Ant only invokes java.io.File#canWrite so if a file is nonwritable but JVM cannot detect this state, this selector will still select the file.

Executable Selector

The <executable> selector selects only files that are executable. Ant only invokes java.nio.file.Files#isExecutable so if a file is not executable but JVM cannot detect this state, this selector will still select the file.

Since Ant 1.10.0

Symlink Selector

The <symlink> selector selects only files that are symbolic links. Ant only invokes java.nio.file.Files#isSymbolicLink so if a file is a symbolic link but JVM cannot detect this state, this selector will not select the file.

Since Ant 1.10.0

OwnedBy Selector

The <ownedBy> selector selects only files that are owned by the given user. Ant only invokes java.nio.file.Files#getOwner so if a file system doesn't support the operation this selector will not select the file.

Since Ant 1.10.0

PosixGroup Selector

The <posixGroup> selector selects only files that are owned by the given POSIX group. Ant only invokes java.nio.file.Files#readAttributes so if a file system doesn't support the operation or POSIX attributes this selector will not select the file.

Since Ant 1.10.4

PosixPermissions Selector

The <posixPermissions> selector selects only files that have the given POSIX permissions. Ant only invokes java.nio.file.Files#getPosixFilePermissions so if a file system doesn't support the operation this selector will not select the file.

Since Ant 1.10.4

Script Selector

The <scriptselector> element enables you to write a complex selection algorithm in any Apache BSF or JSR 223 supported language. See the Script task for an explanation of scripts and dependencies.

Since Apache Ant 1.7

This selector can take a nested <classpath> element. See the script task on how to use this element.

If no src attribute is supplied, the script must be nested inside the selector declaration.

The embedded script is invoked for every test, with the bean self is bound to the selector. It has an attribute selected which can be set using setSelected(boolean) to select a file.

The following beans are configured for every script, alongside the classic set of project, properties, and targets.

The self bean maps to the selector, which has the following attributes. Only the selected flag is writable, the rest are read only via their getter methods.

Example

<scriptselector language="javascript">
  self.setSelected(true);
</scriptselector>

Selects every file.

<scriptselector language="javascript">
  self.setSelected((filename.length%2)==0);
</scriptselector>

Select files whose filename length is even.

Selector Containers

To create more complex selections, a variety of selectors that contain other selectors are available for your use. They combine the selections of their child selectors in various ways.

The selector containers are:

• <and>—select a file only if all the contained selectors select it.
• <majority>—select a file if a majority of its selectors select it.
• <none>—select a file only if none of the contained selectors select it.
• <not>—can contain only one selector, and reverses what it selects and doesn't select.
• <or>—selects a file if any one of the contained selectors selects it.
• <selector>—contains only one selector and forwards all requests to it without alteration, provided that any "if" or "unless" conditions are met. This is the selector to use if you want to define a reference. It is usable as an element of <project>. It is also the one to use if you want selection of files to be dependent on Ant property settings.

All selector containers can contain any other selector, including other containers, as an element. Using containers, the selector tags can be arbitrarily deep. Here is a complete list of allowable selector elements within a container:

• <and>
• <contains>
• <custom>
• <date>
• <depend>
• <depth>
• <filename>
• <majority>
• <none>
• <not>
• <or>
• <present>
• <selector>
• <size>

And Selector

The <and> tag selects files that are selected by all of the elements it contains. It returns as soon as it finds a selector that does not select the file, so it is not guaranteed to check every selector.

Here is an example of how to use the And Selector:

<fileset dir="${dist}" includes="**/*.jar">
    <and>
        <size value="4" units="Ki" when="more"/>
        <date datetime="01/01/2001 12:00 AM" when="before"/>
    </and>
</fileset>

Selects all the JAR file larger than 4096 bytes which haven't been update since the last millennium.

Majority Selector

The <majority> tag selects files provided that a majority of the contained elements also select it. Ties are dealt with as specified by the allowtie attribute.

Here is an example of how to use the Majority Selector:

<fileset dir="${docs}" includes="**/*.html">
    <majority>
        <contains text="project" casesensitive="false"/>
        <contains text="taskdef" casesensitive="false"/>
        <contains text="IntrospectionHelper" casesensitive="true"/>
    </majority>
</fileset>

Selects all the HTML files which contain at least two of the three phrases project, taskdef, and IntrospectionHelper (this last phrase must match case exactly).

None Selector

The <none> tag selects files that are not selected by any of the elements it contains. It returns as soon as it finds a selector that selects the file, so it is not guaranteed to check every selector.

Here is an example of how to use the None Selector:

<fileset dir="${src}" includes="**/*.java">
    <none>
        <present targetdir="${dest}"/>
        <present targetdir="${dest}">
            <mapper type="glob" from="*.java" to="*.class"/>
        </present>
    </none>
</fileset>

Selects only .java files which do not have equivalent .java or .class files in the dest directory.

Not Selector

The <not> tag reverses the meaning of the single selector it contains.

Here is an example of how to use the Not Selector:

<fileset dir="${src}" includes="**/*.java">
    <not>
        <contains text="test"/>
    </not>
</fileset>

Selects all the files in the src directory that do not contain the string test.

Or Selector

The <or> tag selects files that are selected by any one of the elements it contains. It returns as soon as it finds a selector that selects the file, so it is not guaranteed to check every selector.

Here is an example of how to use the Or Selector:

<fileset dir="${basedir}">
    <or>
        <depth max="0"/>
        <filename name="*.png"/>
        <filename name="*.gif"/>
        <filename name="*.jpg"/>
    </or>
</fileset>

Selects all the files in the top directory along with all the image files below it.

Selector Reference

The <selector> tag is used to create selectors that can be reused through references. It is the only selector which can be used outside of any target, as an element of the <project> tag. It can contain only one other selector, but of course that selector can be a container.

The <selector> tag can also be used to select files conditionally based on whether an Ant property exists or not. This functionality is realized using the if and unless attributes in exactly the same way they are used on targets or on the <include> and <exclude> tags within a <patternset>.

Here is an example of how to use the Selector Reference:

<project default="all" basedir="./ant">

    <selector id="completed">
        <none>
            <depend targetdir="build/classes">
                <mapper type="glob" from="*.java" to="*.class"/>
            </depend>
            <depend targetdir="docs/manual/api">
                <mapper type="glob" from="*.java" to="*.html"/>
            </depend>
        </none>
    </selector>

    <target>
        <zip>
            <fileset dir="src/main" includes="**/*.java">
                <selector refid="completed"/>
            </fileset>
        </zip>
    </target>

</project>

Zips up all the java files which have an up-to-date equivalent class file and javadoc file associated with them.

And an example of selecting files conditionally, based on whether properties are set:

<fileset dir="${working.copy}">
    <or>
        <selector if="include.tests">
            <filename name="**/*Test.class">
        </selector>
        <selector if="include.source">
            <and>
                <filename name="**/*.java">
                <not>
                    <selector unless="include.tests">
                        <filename name="**/*Test.java">
                    </selector>
                </not>
            </and>
        </selector>
    </or>
</fileset>

A fileset that conditionally contains Java source files and Test source and class files.

Custom Selectors

You can write your own selectors and use them within the selector containers by specifying them within the <custom> tag.

First, you have to write your selector class in Java. The only requirement it must meet in order to be a selector is that it implements the org.apache.tools.ant.types.selectors.FileSelector interface, which contains a single method. See Programming Selectors in Ant for more information.

Once that is written, you include it in your build file by using the <custom> tag.

Here is how you use <custom> to use your class as a selector:

<fileset dir="${mydir}" includes="**/*">
    <custom classname="com.mydomain.MySelector">
        <param name="myattribute" value="myvalue"/>
    </custom>
</fileset>

A number of core selectors can also be used as custom selectors by specifying their attributes using <param> elements. These are

• Contains Selector with classname org.apache.tools.ant.types.selectors.ContainsSelector
• Date Selector with classname org.apache.tools.ant.types.selectors.DateSelector
• Depth Selector with classname org.apache.tools.ant.types.selectors.DepthSelector
• Filename Selector with classname org.apache.tools.ant.types.selectors.FilenameSelector
• Size Selector with classname org.apache.tools.ant.types.selectors.SizeSelector

Here is the example from the Depth Selector section rewritten to use the selector through <custom>.

<fileset dir="${doc.path}" includes="**/*">
    <custom classname="org.apache.tools.ant.types.selectors.DepthSelector">
        <param name="max" value="1"/>
    </custom>
</fileset>

Selects all files in the base directory and one directory below that.

For more details concerning writing your own selectors, consult Programming Selectors in Ant.