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• name
  The name of the dynamic variable used to refer to it.
• checkonce:= "true" | "false" (optional, defaults to "false")
  Mark the dynamic variable to be evaluated just once, either when the installation starts or as soon as an optional condition gets true. This makes it behave like a normal variable, although with enhanced capabilities to gather a value.
  Values gathered by a dynamic variable definition with checkonce="true" can be overridden, if there is another dynamic variable with the same key (and different conditions which evaluate to  true ) found later.
• ignorefailure:= "true" | "false" (optional, defaults to "true")
  Might be used to allow the installation to continue or abort if an error occurred during gathering the value for a certain dynamic variable.
• condition (optional)
  The assignment of a dynamic variable itself can be made dependent on a certain condition, using the condition attribute, which refers to the ID of condition defined in the installer description elsewhere.
• unset:= "true" | "false" (optional, defaults to "true")
  By defaut, if none of the conditions of a dynamic variable of one and the same name isn't met, a dynamic variable is unset for cleanup purposes.
  Setting unset false prevents unsetting a variable if the complex condition above is not met and leaves the variable value unchanged for that definition.

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<dynamicvariables>

    <variable name="XML_Comment_Start" condition="\!izpack.selected.mycoolfeature">
        <value><\!\[CDATA[<!--]\]></value>
    </variable>
    <variable name="XML_Comment_End" condition="\!izpack.selected.mycoolfeature">
        <value><\!\[CDATA[-->]\]></value>
    </variable>

    <variable name="XML_Comment_Start" value="" condition="izpack.selected.mycoolfeature" />
    <variable name="XML_Comment_End" value="" condition="izpack.selected.mycoolfeature" />

</dynamicvariables>

The condition "izpack.selected.mycoolfeature"

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The condition "izpack.selected.mycoolfeature" is generated automatically when a pack with the ID "mycoolfeature" was specified. You could now use ${XML_Comment_Start} and ${XML_Comment_End} in a file which should be parsed.

is generated automatically when a pack with the ID "mycoolfeature" was specified. You could now use ${XML_Comment_Start} and ${XML_Comment_End} in a file which should be parsed.

For example, there might be an input file test.xml installed to ${INSTALL_PATH}:

<?xml version="1.0"?>
<test>
	<a></a>
	${XmlCommentStart}<b></b>${XmlCommentEnd}
</test>

parsed like this in install.xml:

<parsable targetfile="$INSTALL_PATH/test.xml" encoding="UTF-8"/>

If the pack mycoolfeature would be enabled during the installation, the file would look like this at the end:

<?xml version="1.0"?>
<test>
	<a></a>
	<b></b>
</test>

otherwise the <b></b> element would be commented out:

<?xml version="1.0"?>
<test>
	<a></a>
	<!-- <b></b> -->
</test>

Values from Environment Variables

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<dynamicvariables>
   <variable ... <!-- other nested arguments might go here -->
      <filters>
         <filter1 .../>
         <filter2 .../>
         ... <!-- more filters might go here -->
      </filters>
   </variable>
</dynamicvariable>

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Regular Expression Filter

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