ProcessBuilder not displaying output stream if it is java

Question

I got a code which is running and displaying output successfully if I am executing something like "dir" but not displaying the output if I am running "java -version" or other command from java. Please help:

public static void execJob(){

    try{        

    ProcessBuilder pb = new ProcessBuilder("C:\\myPrograms\\jdk1.7.0_79\\bin\\java.exe", "-version");
    pb.directory(new File("src"));
    Process process = pb.start();
    IOThreadHandler outputHandler = new IOThreadHandler(process.getInputStream());
    outputHandler.start();
    process.waitFor();

    System.out.println(outputHandler.getOutput());
    }catch(Exception e) {
        System.out.println(e.toString());
    }

}

private static class IOThreadHandler extends Thread {
    private InputStream inputStream;
    private StringBuilder output = new StringBuilder();

    IOThreadHandler(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    public void run() {
        Scanner br = null;
        try {
            br = new Scanner(new InputStreamReader(inputStream));
            String line = null;
            while (br.hasNextLine()) {
                line = br.nextLine();
                output.append(line + System.getProperty("line.separator"));
            }
        } finally {
            br.close();
        }
    }

Try ProcessBuilder.inheritIO(), check that it's writing to stdout and not stderr. — Elliott Frisch
– Elliott Frisch, Commented Oct 7, 2015 at 13:02
Thanks Elliott but inheritIO() didn't help. Any other suggestions.. — Affi
– Affi, Commented Oct 7, 2015 at 13:06

wero · Accepted Answer · 2015-10-07 13:09:07Z

4

java -version writes to stderr, so you need pb.redirectErrorStream(true); to capture the output.

 ProcessBuilder pb = new ProcessBuilder("C:\\myPrograms\\jdk1.7.0_79\\bin\\java.exe", "-version");
 pb.redirectErrorStream(true);
 ...

edited Oct 7, 2015 at 13:09

answered Oct 7, 2015 at 13:03

wero

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1 Comment

Affi Over a year ago

Yes you are right, it is writing now. Actually I am trying to do run java programs from command line and display the output live and it is not displaying the output which is very important. why calling some jar and displaying output not working even if java version is working now. Any idea

Miss Chanandler Bong · Accepted Answer · 2020-04-16 11:01:35Z

-1

private static class IOThreadHandler extends Thread {
    private InputStream inputStream;
    private StringBuilder output = new StringBuilder();
    IOThreadHandler(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    public void run() {
        try (Scanner br = new Scanner(new InputStreamReader(inputStream))) {
            String line = null;
            while (br.hasNextLine()) {
                line = br.nextLine();
                output.append(line).append(System.getProperty("line.separator"));
            }
        }
    }

    public String getOutput() {
        return output.toString();
    }
}

edited Apr 16, 2020 at 11:01

Miss Chanandler Bong

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answered Apr 16, 2020 at 10:39

Sergio

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