I'm setting this ticket type initially to "enhancement" because I feel it may have been deliberate to have the "passthru" attribute behave the way it does in phing 2.3.0.
However, it was a bit misleading to me for when I searched for some way to have ExecTask allow the shell command it was executing to stream the command output to stdout. The "passthru" attribute seems to only change the output of the shell command after all of it has been collected in a buffer because it makes use of the PHP function "exec":
http://us2.php.net/manual/en/function.exec.php
I'd like to propose that the "passthru" attribute when set to "true" make use of the PHP function "passthru":
http://us2.php.net/manual/en/function.passthru.php
Because there are many situations where the command that is executed by ExecTask may prompt the user for input and because of the behaviour of "exec", the user sees no prompt until the buffer has been flushed to stdout.
Let me know if you need a patch to the ExecTask code or if you need more details on the request for enhancement.
Cheers,
Andrew