Ben, welcome to JavaRanch!
Quoting from the
Ant manual, the exec task:
Note that you cannot interact with the forked program, the only way to send input to it is via the input and inputstring attributes.
This means that you must provide either an 'input' or an 'inputstring' attribute to the exec task, and that information will be then passed to the app that is run. In other words, you must provide canned input. Perhaps something like this: