Java Process print output while running

Question

I am trying to run split command in a Java program. When I run it in the console with argument --verbose, it prints the generated chunk as follows:

creating file 'chunk00'
creating file 'chunk01'
creating file 'chunk02'

But when I run it in a java program, these outputs will be printed after finishing the process. What I must do to get outputs while split process is running?

I've used the following code:

ProcessBuilder pb = new ProcessBuilder("split", "-a 2", "-d", "-b 52MB","--verbose",path+"/"+db,"chunk");
        pb.redirectErrorStream(true);
        File workingFolder = new File("/home/hajibaba");
        pb.directory(workingFolder);
        Process proc = pb.start();
        BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));

        // read the output from the command
        String s = null;
        while ((s = stdInput.readLine()) != null)
        {
            System.out.println(s);
        }
        proc.waitFor();

However, it works for a bash script that uses echo for print same results.

You must also split the "-a 2" to "-a", "2", also "-b 52MB" to "-b", "52MB" — Balazs Vago
– Balazs Vago, Commented Mar 1, 2017 at 11:24

Community · Accepted Answer · 2017-04-13 12:36:27Z

1

I/O is line buffered in an interactive session but buffered when writing to a pipe.

To work around the problem you can turn off buffering with the unbuffer command.

ProcessBuilder pb = new ProcessBuilder("unbuffer", "split", "-a2", "-d", "-b52MB","--verbose",path+"/"+db,"chunk");

https://unix.stackexchange.com/questions/25372/turn-off-buffering-in-pipe

edited Apr 13, 2017 at 12:36

CommunityBot

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answered Mar 1, 2017 at 11:29

Klas Lindbäck

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