setOut() and redirectOutput() together (original) (raw)

Peter Levart peter.levart at gmail.com
Thu May 28 13:43:30 UTC 2015

That's right.

System.setOut(OutputStream) only assigns some OutputStream object to the System.out field, so any Java code using System.out to retrieve the OutputStream will use the newly set OuputStream. ProcessBuilder.Redirect.INHERIT on the other hand, tells ProcessBuilder where to redirect the standard output of the subprocess when it is started. This has nothing to do with System.out field except that by default the field holds an OutputStream object that outputs to the standard output of the java process and that is also where ProcessBuilder.Redirect.INHERIT instructs ProcessBuilder to redirect the output of the started subprocess (inherits the output of the java process). In other words: the "target" of the default System.out and subprocess redirected output when using ProcessBuilder.Redirect.INHERIT is the same. When you change System.out, you change it's target, but that doesn't change where ProcessBuilder.Redirect.INHERIT redirects to.

Regards, Peter

On 05/28/2015 12:48 PM, Dawid Weiss wrote:

Your code makes the native app inherit native stdout/err process descriptors, you need to pipe the output from your native app to Java and then redirect the output to wherever you wish (byte array for example).

In other words, Redirect.PIPE + pipe code. Dawid On Thu, May 28, 2015 at 12:43 PM, Weijun Wang <weijun.wang at oracle.com> wrote: I am writing something like this

ByteArrayOutputStream bout = new ByteArrayOutputStream(); System.setOut(out); System.out.println("Hello"); ProcessBuilder pb1 = new ProcessBuilder("./native-app"); pb1.redirectOutput(ProcessBuilder.Redirect.INHERIT); pb1.start(); Now "Hello" no longer shows on screen, but the output of "native-app" still shows up there. What else shall I do? This is Ubuntu 14.04.2. Thanks Max

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