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Java process is failing when I attempt to capture stderr

Posted on 2011-02-23
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Last Modified: 2013-11-13
I am attempting to capture the stderr output of ffmpeg (see the sample code below). I have no problem capturing sdtout but the application hangs when I attempt to read stderr.

 try {
//banner is written to stderr
                 ProcessBuilder pb = new ProcessBuilder("c:\\bin\\ffmpeg.exe","-h");
                  
                  String line;
                  Process p = pb.start();
                  BufferedReader input =
                    new BufferedReader
                      (new InputStreamReader(p.getInputStream()));
                  while ((line = input.readLine()) != null) {
                    System.out.println(line);
                  }
                  BufferedReader input1 =
                          new BufferedReader
                            (new InputStreamReader(p.getErrorStream()));
                        while ((line = input1.readLine()) != null) {
                          System.out.println(line);
                        }
                 
                  input.close();
                }
                catch (Exception err) {
                  err.printStackTrace();
                }
             

I tried c# and it worked as expected

 see below


            string error;
            string output;
            ProcessStartInfo psi = new ProcessStartInfo(@"c:\signal\publisher\bin\ffmpeg.exe", "-h");
            psi.RedirectStandardOutput = true;
            psi.RedirectStandardError = true;
            System.Diagnostics.Process reg;
            psi.UseShellExecute = false;    
            reg = System.Diagnostics.Process.Start(psi);
            using (System.IO.StreamReader myOutput = reg.StandardOutput)
            { output = myOutput.ReadToEnd(); }
            using (System.IO.StreamReader myError = reg.StandardError)
            { error = myError.ReadToEnd(); }
            Console.WriteLine(error);
          //  Console.WriteLine(output);
            Console.ReadKey();

Any idea's why this doesn't work in java?
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Question by:JonMny
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3 Comments
 
LVL 92

Accepted Solution

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objects earned 2000 total points
ID: 34966378
you'll need to read it in a separate thread
http://helpdesk.objects.com.au/java/runtime-exec-locks-up
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LVL 9

Author Comment

by:JonMny
ID: 34966743
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LVL 92

Expert Comment

by:objects
ID: 34966844
should really find some time to update that code, its getting a little outdated.
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