ProcessBuilder Output hangs on readLine - inputstream

Question

I am trying to run some commands using ProcessBuilder and everything is working fine besides one small detail: in one case I only get the output when the task finishes running. I checked the program, and it is hanging on the first readLine(). I am running it in separate threads and I tried already both merging the input and error streams with "redirectErrorStream(true)" and having them separate with no changes in the mentioned behavior. I also tried to have a while loop that would only do the first readLine() after BufferedReader returning true for ready() but it didn't work (maybe not a very clever solution but I am trying everything to understand what is going on...)
The code works perfectly with some executables, giving output while it's running, but in some cases hangs on the first readline()... Someone has any idea what might cause that and how to solve it?
It is a little strange for me, given that when I execute the same command in the command prompt the output is shown while the program is running.
This question seems the same as the one I found in other threads but I couldn't find a solution for this in any of them.
Here is the code I am using, based on (http://thilosdevblog.wordpress.com/2011/11/21/proper-handling-of-the-processbuilder/):
List<String> command = new ArrayList<String>();
command.add(%COMMAND1)
command.add(%COMMAND2)
...
ProcessBuilderWrapper pbd = new ProcessBuilderWrapper(command);
ProcessBuilderWrapper:
public class ProcessBuilderWrapper {
public ProcessBuilderWrapper(File directory, List command) throws Exception {
ProcessBuilder pb = new ProcessBuilder(command);
if (directory != null) {
pb.directory(directory);
}
pb.redirectErrorStream(true);
Process process = pb.start();
StreamBoozer seInfo = new StreamBoozer(process.getInputStream());
seInfo.start();
}
public ProcessBuilderWrapper(List command) throws Exception {
this(null, command);
}
}
StreamBoozer:
public class StreamBoozer extends Thread {
private InputStream in;
StreamBoozer(InputStream in) {
this.in = in;
}
#Override
public void run() {
BufferedReader br = null;
br = new BufferedReader(new InputStreamReader(in));
try {
String line = null;
while ((line = br.readLine()) != null) { <<<<<<<<<<<<< It hangs here #####
System.out.println(line);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Thank you!

Answer 1

I think you misunderstand the building of the list command. The list can't be use for more than 1 command. That means, you can run one command only with ProcessBuilderWrapper.
Have as look at the Javadoc of the ProcessBuilder:
command - a string array containing the program and its arguments
E.g. for 'ls -al' you should use:
List command = new ArrayList();
command.add("ls");
command.add("-al");
If you are using the SteamBoozer-stuff Process,waitFor and SteamBoozer.join should be used (look at the blog article you mentioned above). Otherwise you could run into ugly timing issues! This can lead to the strange behavior you described above.
Regards
Thilo