Collecting output from Docker in java application

Question

I'm executing some code on docker in my java application using ProcessBuilder to run the code, however i'm having trouble retrieving the output from it. BufferedReader is not reading anything from the InputStream returned from the container. Is there a specific way to retrieve output from Docker?? I've never had trouble getting output from bash executions before, so I'm thinking maybe docker does things differently somehow. Any ideas would be appreciated

Here's a snippet of the code:

    Process dockerCommand;
    ProcessBuilder builder = new ProcessBuilder("bash","-c","sudo docker images");
    builder.redirectErrorStream(true);
    builder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
    builder.redirectError(ProcessBuilder.Redirect.INHERIT);
    dockerCommand = builder.start();       

    dockerCommand.waitFor();

    List<String> result = new ArrayList<>();
    try (BufferedReader reader = new BufferedReader(new InputStreamReader(dockerCommand.getInputStream()))
    {
        String line = reader.readLine();
        while (line != null) {
            result.add(line);
            line = reader.readLine();
        }
    } 
    catch (IOException exc) 
    {}

Answer 1

The line

builder.redirectOutput(ProcessBuilder.Redirect.INHERIT);

causes bash to receive the same standard output as the parent process, which is presumably your terminal window. This produces misleading results because you actually see the Docker image list, but it's being printed by the shell.

If I comment that out and then iterate over the results list, I can see the output from Docker inside the JVM.