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From "KUMAR,PANKAJ (HP-Cupertino,ex1)" <>
Subject FW: How to execute an interactive non-java program from an ant sc ript ?
Date Wed, 15 May 2002 01:07:39 GMT
Forwarding to ant-dev as I didn't hear any suggestion on ant-user.

Pankaj Kumar.

PS: Please CC to me if you respond as I am not subscribed to ant-dev.

> -----Original Message-----
> From:	KUMAR,PANKAJ (HP-Cupertino,ex1) 
> Sent:	Monday, May 13, 2002 4:07 PM
> To:	''
> Subject:	How to execute an interactive non-java program from an ant
> script ?
> Hi,
> I have a need to launch a text mode interactive non-java application that
> prompts user for text input . I looked at Exec task ( in Ant1.5Beta1 ) and
> found that this doesn't take care of passing user input to the created
> process. To address this I wrote a new task named ExecInteractive  by
> deriving it from ExecTask and supplying my own MyPumpStreamHandler class
> (implementing from ExecStreamHandler ). This handler creates three
> separate threads that write the normal output of the new process to
> System.out, error output to System.err and input from to the
> OutputStream associated with the process. The code run by each thread is
> in class MyStreamPumper modeled after StreamPumper class ( all these are
> in packacge org.apache.ant.taskdefs ).
> This works okay but with following problems:
> 1. Whenever the external program prompts the user for input and terminates
> the prompt string without a newline then nothing gets written on the
> terminal. I changed my code in MyStreamPumper so that it would call
> System.out.flush() after writing each byte. However, this causes each
> character to be written on a separate line !! I beleive Ant is processing
> output through System.out and takes System.out.flush() as indication of
> record termination.
> I have an ugly workaround for the time being -- I wrote a class AntWrapper
> that grabs the System.out and in static variable and then
> invokes the main() of Ant. I use these static variables in my
> MyStreamPumper. To invoke ant, I call "java <package>.AntWrapper ...".
> Would prefer a better solution.
> 2. The second problem is more insidious. As I mentioned earlier,
> MyPumpStreamHandler creates three threads: one for monitotring stdout of
> the external program, one for stderr of the external program and one for
> keyborad input ( by reading ). When the external program
> terminates then the thread monitoring the stdout and stderr of the process
> terminate but not the thread that is waiting for input on The
> thread executing ExecStreamHandler is able to do a Thread.join() with
> these two threads but is not able to interrupt the thread waiting for
> keyboard input.
> My workaround is to ask the user ( from thread running the
> MyPumpStreamHandler ) to hit ENTER. When the waiting thread reads this and
> tries to write to the stdin of the terminated process, it gets exception
> and terminates itself.
> But I don't like this as it forces the user to do something unnecessary.
> Any help is most appreciated.
> Pankaj Kumar,
> HP Middleware.

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