See the following class below, I use it to read the output from any of the processes that are added to it. At the moment I'm starting up a Jar that acts as a channel adapter between the C# application and a JMS messaging broker. The only problem is, that when reading from the StandardOutput
of the process the thread blocks on the reader.Peek()
call.
After some debugging I found out that this only happens if no output has been written to the StandardOutput
stream of the process. I've played around a bit with the immediate window to figure out if I can find a way to determine whether the underlying stream is empty. But so far all calls to properties like Stream.CanRead
or FileStream.Length
throw InvalidOperationExceptions
or return output that cannot be used to check for this condition.
Furthermore, I also tried using the OutputDataReceived
and ErrorDataReceived
events, but for some reason they never seem to fire.
So my question is; is there any way that can be used to cleanly read the output from the processes as it becomes available?
The class in which the output is read:
namespace ReparatieSysteem.Lib
{
internal delegate void NewOutputLineEvent(Process process, int port, string line);
class ProcessListener
{
private static readonly Dictionary<int, Process> processes;
private static readonly Thread thread;
static ProcessListener()
{
processes = new Dictionary<int, Process>();
thread = new Thread(RunThread);
thread.Start();
}
private static void PollProcesses()
{
foreach (var item in processes.Where(p => p.Value.HasExited).ToList())
{
processes.Remove(item.Key);
}
foreach (var item in processes)
{
SendLines(item.Value, item.Key, ReadReader(item.Value.StandardError));
SendLines(item.Value, item.Key, ReadReader(item.Value.StandardOutput));
}
}
private static void SendLines(Process process, int port, IEnumerable<String> lines)
{
foreach(var line in lines)
{
if (OnNewOutput != null)
{
OnNewOutput(process, port, line);
}
}
}
private static IEnumerable<string> ReadReader(StreamReader reader)
{
while (reader.Peek() >= 0)
{
yield return reader.ReadLine();
}
}
private static void RunThread()
{
while(true)
{
if (processes.Count > 0)
{
PollProcesses();
}
Thread.Sleep(200);
}
}
public static void AddProcess(int port, Process process)
{
processes.Add(port, process);
}
public static event NewOutputLineEvent OnNewOutput;
}
}
The code that creates the process:
var procStartInfo = new ProcessStartInfo("java",
string.Format("-jar {0} {1} {2} {3}", JarPath, ConnectionName, _listenQueue, _listenPort))
{
RedirectStandardOutput = true,
RedirectStandardError = true,
UseShellExecute = false,
CreateNoWindow = true
};
_brokerProcess = new Process { StartInfo = procStartInfo };
_brokerProcess.Start();
ShutdownListener.OnApplicationQuit += _brokerProcess.Kill;
ProcessListener.AddProcess(_listenPort, _brokerProcess);
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