进程循环运行，而不是每次都记录日志

Question

I have a class in which I can run rsync commands from a shell script.

It all works as it should, except when logging the process output (instream and error stream) to file.

I have a loop in my class which allows 5 runs if the process fails, and in each run every stream/writer/reader is initialised and closed completely.

The problem is that the file is only written to once or twice in the 5 runs, and it's never the same runs that are output. I set a 10 second sleep after the process to make the output more readable and I could see the only output being written to file was after 20 and 30 seconds, or after 10 and 40 seconds etc.

Every output from the process in written to console but not to file.

My code is as follows. Any advice would be appreciated.

private static void run() throws IOException {
    while (retry && NUMBER_OF_TRIES >= tries){
        InputStream in = null;
        PrintStream out = null;
        InputStream errIn = null;

        try {
            // get runtime object to run cmd
            Runtime RT = Runtime.getRuntime();

            Process PR = RT.exec( cmd );
            errIn = PR.getErrorStream();
            in = PR.getInputStream();
            out = new PrintStream(new FileOutputStream(new File(output), true));
            System.out.println("file output initialised");
            StreamGobbler inConsumer = new StreamGobbler( in, new Date() + " OUTPUT: ", out );
            StreamGobbler errConsumer = new StreamGobbler( errIn, new Date() + " ERROR: ", out );
            System.out.println("Starting consumer threads");
            inConsumer.start();
            errConsumer.start();

            Thread.sleep(10000);

            int exitVal = PR.waitFor();
            if (exitVal > 0){
                retry = true;
                tries++;
            } else {
                retry = false;
            }
            System.out.println("ExitValue: " + exitVal);

            // Wait for the consumer threads to complete
            inConsumer.join();
            errConsumer.join();         

        } catch ( Exception e ) {

            e.printStackTrace();
            System.out.println( "failed: " + e.getMessage() );
        } finally {
            // the StreamConsumer classes will close the other streams
            if ( out != null ){
                out.close();
            }
            if (in != null){
                in.close();
            }
            if (errIn != null){
                errIn.close();
            }               
        }
    }
}

Answer 1

i don't ever see your printstream object "out" ever being used besides it getting initialized. If you want to write to the file you should call the printstream object.

System.out.println("ExitValue: " + exitVal);
//now call the printstream object
out.print("ExitValue: " + exitVal);
//flushing will force the string to be written to the file
out.flush();

You can follow the above code everytime you write to console and you want to write to the file you created your printstream object with.