You need to read the output (and error) streams from the Process using getInputStream() and getErrorStream(). You’ll need a separate thread for this if you want to wait for the process to complete.

String[] cmd = {"java", "-cp", "C:/Users/..../workspace/Testing/bin", s, str};
Process p = new ProcessBuilder(cmd).redirectErrorStream(true).start();
final InputStream pOut = p.getInputStream();
Thread outputDrainer = new Thread()
{
    public void run()
    {
        try
        {
            int c;
            do
            {
                c = pOut.read();
                if (c >= 0)
                    System.out.print((char)c);
            }
            while (c >= 0);
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }
};
outputDrainer.start();

p.waitFor();

If you are using Java 7 and want all output of the process to be redirected to the console, the code is considerably simpler:

String[] cmd = {"java", "-cp", "C:/Users/..../workspace/Testing/bin", s, str};
Process p = new ProcessBuilder(cmd).redirectError(Redirect.INHERIT)
                                   .redirectOutput(Redirect.INHERIT)
                                   .start();
p.waitFor();

The redirectError() and redirectOutput() methods with Redirect.INHERIT cause output to just be sent to the parent Java process.

Here is the way to go:

Runtime rt = Runtime.getRuntime();
String[] commands = {"system.exe", "-get t"};
Process proc = rt.exec(commands);

BufferedReader stdInput = new BufferedReader(new 
     InputStreamReader(proc.getInputStream()));

BufferedReader stdError = new BufferedReader(new 
     InputStreamReader(proc.getErrorStream()));

// Read the output from the command
System.out.println("Here is the standard output of the command:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
    System.out.println(s);
}

// Read any errors from the attempted command
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
    System.out.println(s);
}

Read the Javadoc for more details here. ProcessBuilder would be a good choice to use.

You have different system environment in executing from command string and executing from Eclipse.

Variables of environment are valuable : PATH, JAVA_HOME or JRE_HOME and your current worikng directory.

I use ProcessBuilder in cases, when I must be sure in environment, that is provided for external process like yours "java CPU/memory".

I think that first of all your external process have wrong working directory. In ProcessBuilder you can point on it with:

ProcessBuilder pb = new ProcessBuilder("java", "CPU/MEMORY");   
pb.directory(new File("/home/myhome/myjavaprojects"));
Process p = pb.start();

You need to capture both the std out and std err in the process. You can then write std out to a file/mail or similar.

See this article for more info, and in particular note the StreamGobbler mechanism that captures stdout/err in separate threads. This is essential to prevent blocking and is the source of numerous errors if you don't do it properly!

The standard output of Runtime.exec is not automatically sent to the standard output of the caller.

Something like this aught to do - get access to the standard output of the forked process, read it and then write it out. Note that the output from the forked process is availble to the parent using the getInputStream() method of the Process instance.

Copypublic static void main(String[] args) throws Exception {
    System.setOut(new PrintStream(new FileOutputStream("test.txt")));
    System.out.println("HelloWorld1");

     try {
       String line;
       Process p = Runtime.getRuntime().exec( "echo HelloWorld2" );

       BufferedReader in = new BufferedReader(
               new InputStreamReader(p.getInputStream()) );
       while ((line = in.readLine()) != null) {
         System.out.println(line);
       }
       in.close();
     }
     catch (Exception e) {
       // ...
     }
}