<tool id="unique_line" name="unique_line">
  <description>remove duplicate lines</description>
  <command> cat $input | sort | uniq > $output </command>
  <inputs>
    <param name="input" format="txt" type="data" label="Original file"/>
  </inputs>
  <outputs>
    <data format="input" name="output" />
  </outputs>
</tool>