Question

In a long running Ant script, I have a target that gets called roughly once per second. (This is probably not a good thing, but let’s accept it for the moment.)
I only want it to execute if its last actual execution was at least five minutes ago.

One idea for a solution is to maintain a lastRunTimestamp property, and compare the current time to that.

Problem: How can I compare timestamps in Ant?

Another solution that would also be welcome is a means of executing the target only at specified time intervals, so that the check would not be necessary.

I am using Ant 1.7.1 and ant-contrib.

Any ideas are greatly appreciated – thanks!

Answer 1

Interesting question, and one which is a bit harder to answer than I originally thought.

You can use the <tstamp> task to set a time stamp that’s five minutes old:

<tstamp>
  <format property="time_stamp"
      offset="-5"
      unit="minutes"
      pattern="MM/dd/yyyy hh:mm:ss aa"/>
</tstamp>

Once you have that timestamp, you can use the lastmodified condition of the <condition> task to see if a particular file has been updated since. If you don’t have a file, you can use the <touch> task to create one.

<condition property="has.been.modified">
     <islastmodified dateTime="${time_stamp}" mode="after">
        <file file="${touch.file}"/>
     </islastmodified>
</condition>

The only issue is that default properties are immutable. Once set, you can’t change them. Fortunately you’re using ant-contrib and ant-contrib allows you to change that via the variable task.