BufferedReader.read() blocks,when checking if there's any input

[angelotti]

Hi everyone ,

i have the following problem , i read data from another application that i started through the runtime.exec() in my Java class. I need to periodically check if there is any data sent from it but when i try to BufferedReader.read() from the stream and the stream is empty the java app blocks ,supposably waiting for either the child process to end or for any data to be sent....

Both scenarios does not work for me and so can anyone please tell me the following:

- how to check if there is any data sent by the cild process without blocking the parent???

thanks a lot in advance , anyone...?

[dmjpro]

Hi everyone ,

i have the following problem , i read data from another application that i started through the runtime.exec() in my Java class. I need to periodically check if there is any data sent from it but when i try to BufferedReader.read() from the stream and the stream is empty the java app blocks ,supposably waiting for either the child process to end or for any data to be sent....

Both scenarios does not work for me and so can anyone please tell me the following:

- how to check if there is any data sent by the cild process without blocking the parent???

thanks a lot in advance , anyone...?

The picture is not clear to me....
plz send ur code .....

kind regards,
dmjpro.

[angelotti]

Hi, here's some code to make it clear:

String[] command={"prog.exe"};
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec(command);

InputStreamReader new_isr = new InputStreamReader(proc.getInputStream());
BufferedReader new_br = new BufferedReader(new_isr);
int new_line = 0;

if ( (new_line = new_br.read()) != -1)// Here's the problem
System.out.println((char)new_line);

The problem is that new_br.read() blocks when called if there is nothing to read in the stream. Normally the stream would send -1 when closed but i need to keep it open and check periodically if there is something sent in it.

When i try and do it this way the new_br.read() blocks when the stream is empty and thus my program hangs until prog.exe is forcably terminated...

I wantes to know if there is another way to check if there is data sent to the stream.

thanks in advance

[JosAH]

There was no need to start a new thread for your question. If you want more
attention, simply 'bump' your other thread. The problem is that you're just using
one single thread for reading/writing and to control your child process.

On top of that, you're using a buffered reader which attempts to read line by line
or worse. Your C process writes a last line without the newline at the end. Your
buffered reader keeps on attempting to read more from the child process but
there isn't any. When the child process stops your buffered reader receives
the <eof> condition and un-blocks.

kind regards,

Jos

[angelotti]

There was no need to start a new thread for your question. If you want more
attention, simply 'bump' your other thread. The problem is that you're just using
one single thread for reading/writing and to control your child process.

On top of that, you're using a buffered reader which attempts to read line by line
or worse. Your C process writes a last line without the newline at the end. Your
buffered reader keeps on attempting to read more from the child process but
there isn't any. When the child process stops your buffered reader receives
the <eof> condition and un-blocks.

kind regards,

Jos

Thanks to u all, i was aware of the problems and i have already found the solutions:)

[JosAH]

Thanks to u all, i was aware of the problems and i have already found the solutions:)

Good; care to share your solution with us?

kind regards,

Jos