Process (python script -> py2exe ) InputStream is NULL until Process ends

Question

I am trying to catch on fly Process output like below:

new Thread() {
    public void run() {

        final ProcessBuilder builder = new ProcessBuilder("cmd.exe", "/c", "myexec.exe");

        p = builder.start();

        InputStream i = p.getInputStream();
        Reader r = new InputStreamReader(i, "US-ASCII");

        int ch = 32;

        do {
           System.out.print(ch);
        } while ((ch = r.read()) != -1);

    }
}.start();

As I see, while Process is running ch == null, when Process is terminated all missing chars are suddenly printed.

How can I read output during Process running?

Why ? the same situation is when i use another thread to capture output like: p = builder.start(); StreamGobbler outputGobbler = new StreamGobbler(p.getInputStream()); outputGobbler.start(); — mynameismarcin, Mar 12 '14 at 17:50

score 0 · Answer 1 · answered Mar 12 '14 at 18:41

0

You need to spawn additional thread to consume data from stream and wait for process to complete in main thread:

...
p = builder.start();

new Thread() {
    public void run() {
        InputStream i = p.getInputStream();
        Reader r = new InputStreamReader(i, "US-ASCII");

        int ch = 32;

        do {
            System.out.print(ch);
        } while ((ch = r.read()) != -1);
    }
}.start();

// wait for process to complete while thread above consumes data
p.waitFor();

answered Mar 12 '14 at 18:41

hoaz

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unfortunately it makes no diference..still process output is visible only when process is finished – mynameismarcin Mar 12 '14 at 21:26
Then maybe process produces output right before completion. – hoaz Mar 13 '14 at 02:25

score 0 · Accepted Answer · edited May 23 '17 at 12:21

0

ok i got the solution. myexec.exe was an executable python file produced by py2exe.

due to How to flush output of Python print? i put sys.stdout.flush() after every print function and problem disappeared

edited May 23 '17 at 12:21

Community

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1

answered Mar 13 '14 at 09:06

mynameismarcin

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Process (python script -> py2exe ) InputStream is NULL until Process ends

2 Answers2