Displays all the current properties (or a subset of them specified
by a nested <propertyset>) in the project.  The
output can be sent to a file if desired.  This task can be used as a
somewhat contrived means of returning data from an
<ant> invocation, but is really for debugging build
files.
| Attribute | Description | Required | 
| destfile | If specified, the value indicates the name of the file to send the output of the statement to. The generated output file is compatible for loading by any Java application as a property file. If not specified, then the output will go to the Ant log. | No | 
| prefix | a prefix which is used to filter the properties
        only those properties starting with this prefix will be echoed. 
 | No | 
| failonerror | By default, the "failonerror" attribute is enabled. If an error occurs while writing the properties to a file, and this attribute is enabled, then a BuildException will be thrown, causing the build to fail. If disabled, then IO errors will be reported as a log statement, and the build will continue without failure from this task. | No | 
| format | One of textorxml.
    Determines the output format.  Defaults totext. | No | 
You can specify subsets of properties to be echoed with propertysets.
since Ant 1.6.
<echoproperties/>
Report the current properties to the log.
<echoproperties destfile="my.properties"/>
Report the current properties to the file "my.properties", and will fail the build if the file could not be created or written to.
<echoproperties destfile="my.properties" failonerror="false"/>
Report the current properties to the file "my.properties", and will log a message if the file could not be created or written to, but will still allow the build to continue.
<echoproperties prefix="java."/>
List all properties beginning with "java."
  <echoproperties>
    <propertyset>
      <propertyref prefix="java."/>
    </propertyset>
  </echoproperties>
List all properties beginning with "java."
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