Question: redirectOutput to outputstream

[Panlq]

public class CommandUtilsTest {
    @Test
    public void testPingCommandReadStreamOutput() throws IOException, InterruptedException {
        // Create receivers to capture stdout and stderr
        PipedOutputStream pipedStdout = new PipedOutputStream();
        PipedInputStream pipedStdoutInput = new PipedInputStream(pipedStdout);

        // Start the thread that writes stdout to the PipedOutputStream
        Thread stdoutThread = new Thread(() -> {
            try {
                new ProcessExecutor().command("ping", "www.google.com", "-c",
                        "5")
                        .redirectOutput(pipedStdout)
                        .execute();
                pipedStdout.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (TimeoutException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        });

        // Start the threads to capture the output from the PipedInputStream
        Thread readerThread = new Thread(() -> {
            try (BufferedReader reader = new BufferedReader(new InputStreamReader(pipedStdoutInput))) {
                String line;
                while ((line = reader.readLine()) != null) {
                    // Print to console as it is read (for real-time output)
                    System.out.println(line);
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {

            }
        });

        // Start the stdout capturing thread
        stdoutThread.start();
        readerThread.start();

        // Now, wait for the threads to finish
        readerThread.join();
        stdoutThread.join();

    }

    @Test
    public void testPipeOutputConnected2Input() throws IOException, InterruptedException {
        final PipedOutputStream output = new PipedOutputStream();
        final PipedInputStream input = new PipedInputStream(output);

        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    output.write("Hello Piped Streams!! Used for Inter Thread Communication".getBytes());
                    output.close();

                } catch (IOException io) {
                    io.printStackTrace();
                }
            }
        });

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {

                try (BufferedReader reader = new BufferedReader(new InputStreamReader(input))) {
                    String line;
                    while ((line = reader.readLine()) != null) {
                        System.out.println(line);
                    }
                } catch (IOException io) {
                    io.printStackTrace();
                }

            }
        });

        thread1.start();
        thread2.start();

    }
}

why testPingCommandReadStreamOutput raise error
testPipeOutputConnected2Input well done!

java.io.IOException: Write end dead
	at java.io.PipedInputStream.read(PipedInputStream.java:310)
PipedInputStream.java:310
	at java.io.PipedInputStream.read(PipedInputStream.java:377)
PipedInputStream.java:377
	at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
StreamDecoder.java:284
	at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
StreamDecoder.java:326
	at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
StreamDecoder.java:178
	at java.io.InputStreamReader.read(InputStreamReader.java:184)
	at java.io.BufferedReader.fill(BufferedReader.java:161)
BufferedReader.java:161
	at java.io.BufferedReader.readLine(BufferedReader.java:324)
BufferedReader.java:324
	at java.io.BufferedReader.readLine(BufferedReader.java:389)
CommandUtilsTest.java:163
	at java.lang.Thread.run(Thread.java:750)

[nemecec]

There indeed seems to be an issue when using stream redirection with PipedOutputStream -- zt-exec seems to shut the writing thread down before closing the stream but PipedOutputStream needs the opposite to happen.

As a workaround, I can suggest the following:

        new ProcessExecutor().command("ping", "www.google.com", "-c", "5")
            .redirectOutput(line -> {
              try {
                pipedStdout.write((line + "\n").getBytes(StandardCharsets.UTF_8));
              }
              catch (IOException e) {
                throw new RuntimeException(e);
              }
            })
            .execute();

Basically, handling output line by line and writing it yourself to the PipedOutputStream instance.

[nemecec]

Ok, I investigated this a bit more and found a more elegant solution, see below.

First, you define your own PumpStreamHandler in order to set closeWhenExhausted=true and flushImmediately=true when creating a new pump:

  private static class MyPumpStreamHandler extends PumpStreamHandler {

    public MyPumpStreamHandler(OutputStream outAndErr) {
      super(outAndErr);
    }

    @Override
    protected Thread createPump(InputStream is, OutputStream os) {
      return createPump(is, os, true, true);
    }
  }

And then you use your custom PumpStreamHandler implementation:

        new ProcessExecutor().command("ping", "www.google.com", "-c", "5")
            .streams(new MyPumpStreamHandler(pipedStdout))
            .execute();
        pipedStdout.close();

We should really make this easier to override.