Java Runtime.getRuntime(): getting output from executing a command line program

Question

I'm using the runtime to run command prompt commands from my Java program. However, I'm not aware of how I can get the output the command returns.

Here is my code:

Runtime rt = Runtime.getRuntime();

String[] commands = {"system.exe", "-send" , argument};

Process proc = rt.exec(commands);

I tried doing System.out.println(proc); but that did not return anything. The execution of that command should return two numbers separated by a semicolon. How could I get this in a variable to print out?

Here is the code I'm using now:

String[] commands = {"system.exe", "-get t"};

Process proc = rt.exec(commands);

InputStream stdIn = proc.getInputStream();
InputStreamReader isr = new InputStreamReader(stdIn);
BufferedReader br = new BufferedReader(isr);

String line = null;
System.out.println("<OUTPUT>");

while ((line = br.readLine()) != null)
     System.out.println(line);

System.out.println("</OUTPUT>");
int exitVal = proc.waitFor();
System.out.println("Process exitValue: " + exitVal);

But I'm not getting anything as my output, but when I run that command myself it works fine.

Answer 1

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.