Java Capture all output from a process and log it to file

Question

I'm trying log all output from an Application in java and for some reason it only capturing the first 2 lines i know the application outputs a lot more than this this is my code

logOut = new BufferedWriter(new FileWriter("WebAdmin.log"));

        ProcessBuilder procBuild = new ProcessBuilder(
            "java", "-Xmx1G", "-Xms512M", "-jar", "TekkitServer\\Tekkit.jar", "nogui", "-nojline"
        );
        server = procBuild.start();

        inputStream = new BufferedReader(new InputStreamReader(server.getInputStream()));
        errorStream = new BufferedReader(new InputStreamReader(server.getErrorStream()));
        outputStream = new BufferedWriter(new OutputStreamWriter(server.getOutputStream()));

        String line = "";

        while(!shutdown){
            while((line = inputStream.readLine()) != null){
                logOut.write(line+"\r\n");
                logOut.flush();
                System.out.println(line);
            }
            System.out.println("checking error stream");
            while((line = errorStream.readLine()) != null){
                logOut.write(line+"\r\n");
                logOut.flush();
                System.out.println(line);
            }
        }

        System.out.println("Stoped Reading");
        logOut.close();
        server.destroy();

I'm not even seeing "checking error stream" in my console.

The other lines might going to the errorstream!!!

Vishal K
– Vishal K

2013-03-23 20:42:10 +00:00
Commented Mar 23, 2013 at 20:42 — Vishal K
– Vishal K, Commented Mar 23, 2013 at 20:42

A4L · Accepted Answer · 2013-03-23 20:52:46Z

2

I don't think there is a need for outer while, reading from the output stream blocks until there is some data available, and if the sub process ends you'll get a null and the inner while will break. Also you could use ProcessBuilder's redirectErrorStream(true) to redirect stderr to stdout so you will catch them both in only one loop.

answered Mar 23, 2013 at 20:52

A4L

17.6k6 gold badges53 silver badges76 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

eckes · Accepted Answer · 2013-03-23 20:54:06Z

1

You must read the stdout and stderr streams in its own thread. Otherwise you will get all kinds of blocking situations (depending on operating system and output patterns).

If you merge the error stream with the output stream (redirectErrorStream(true)), you can get along with a single (additional) background thread. You can avoid this, when you use redirectOutput(File) (or inheritIO).

answered Mar 23, 2013 at 20:54

eckes

10.5k1 gold badge66 silver badges74 bronze badges

Collectives™ on Stack Overflow

Java Capture all output from a process and log it to file

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related