Finding hard and soft open file limits from within jvm in linux

Question

Hi All,
I have a problem where I need to find out the hard and soft open file limits for the process in linux from within a java program. When I execute ulimit from the terminal it gives separate values for hard and soft open file limits.
From shell if I run the command then the output is given below:
$ ulimit -n
1024
$ ulimit -Hn
4096
The java program is given below:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
public class LinuxInteractor {
public static int executeCommand(String command, boolean waitForResponse, OutputHandler handler) {
int shellExitStatus = -1;
ProcessBuilder pb = new ProcessBuilder("bash", "-c", command);
pb.redirectErrorStream(true);
try {
Process shell = pb.start();
if (waitForResponse) {
// To capture output from the shell
InputStream shellIn = shell.getInputStream();
// Wait for the shell to finish and get the return code
shellExitStatus = shell.waitFor();
convertStreamToStr(shellIn, handler);
shellIn.close();
catch (IOException e) {
System.out
.println("Error occured while executing Linux command. Error Description: "
+ e.getMessage());
catch (InterruptedException e) {
System.out
.println("Error occured while executing Linux command. Error Description: "
+ e.getMessage());
return shellExitStatus;
public static String convertStreamToStr(InputStream is, OutputHandler handler) throws IOException {
if (is != null) {
Writer writer = new StringWriter();
char[] buffer = new char[1024];
try {
Reader reader = new BufferedReader(new InputStreamReader(is,
"UTF-8"));
int n;
while ((n = reader.read(buffer)) != -1) {
String output = new String(buffer, 0, n);
writer.write(buffer, 0, n);
if(handler != null)
handler.execute(output);
} finally {
is.close();
return writer.toString();
} else {
return "";
public abstract static class OutputHandler {
public abstract void execute(String str);
public static void main(String[] args) {
OutputHandler handler = new OutputHandler() {
@Override
public void execute(String str) {
System.out.println(str);
System.out.print("ulimit -n : ");
LinuxInteractor.executeCommand("ulimit -n", true, handler);
System.out.print("ulimit -Hn : ");
LinuxInteractor.executeCommand("ulimit -Hn", true, handler);
If I run this program the output is given below:
$ java LinuxInteractor
ulimit -n : 4096
ulimit -Hn : 4096
I have used ubuntu 12.04, Groovy Version: 1.8.4 JVM: 1.6.0_29 for this execution.
Please help me in understanding this behavior and how do I get a correct result from withing the java program.

Answer 1

Moderator Action:
As mentioned in one of the earlier responses:
@OP this is not a Java question. I suggest you take it elsewhere, i.e. to a Unix or Linux forum.You posted this to a Java programming forum.
It is not a Java programming inquiry.
This off-topic thread is locked.
Additionally, you have answered your own question.
Don't bother posting it to one of the OS forums. It will get deleted as a duplicate cross-post.