Develop Reference

ProcessBuilder failing when calling a system command where Runtime exec works

I'm having trouble with ProcessBuilder not running a command on the server.
Early in my project I use Runtime.exec() just to retrieve output from a program which works fine:
private List<SatelliteCode> getSatelliteCodes() {
List<SatelliteCode> codes = new ArrayList<>();
Runtime runtime = Runtime.getRuntime();
String[] commands = { "w_scan", "-s?" };
Process process;
try {
process = runtime.exec(commands);
BufferedReader error = new BufferedReader(new InputStreamReader(process.getErrorStream()));
String s = error.readLine(); // discard first line
while ((s = error.readLine()) != null) {
s = s.trim();
int i = s.indexOf('\t'); // separated by a tab!?!?
codes.add(new SatelliteCode(s.substring(0, i), s.substring(i)));
}
} catch (IOException e) {
e.printStackTrace();
}
return codes;
}
Running this in the terminal works fine and I get all the output I need:
w_scan -fs -cGB -sS19E2 > channels.conf
However, the server needs to grab the ongoing output from the 'process.getErrorStream()' to display in the web interface. What is actually happening is the ProcessBuilder is failing and returning an exit code of 1.
The function that initialises the ProcessBuilder and to start the scan running is [EDIT 1]:
private static StringBuilder scan_error_output = null;
#Override
public boolean startSatelliteScan(String user, String country_code, String satellite_code) {
UserAccountPermissions perm = validateUserEdit(user);
if (perm == null) return false;
Shared.writeUserLog(user, Shared.getTimeStamp() +
": DVB satellite scan started " +
country_code + " - " + satellite_code +
System.lineSeparator() + System.lineSeparator());
scan_error_output = new StringBuilder();
new ScanThread(country_code, satellite_code).start();
// write out country code and satellite code to prefs file
BufferedWriter bw = null;
try {
bw = new BufferedWriter(new FileWriter(satellite_last_scan_codes));
bw.write(country_code); bw.newLine();
bw.write(satellite_code); bw.newLine();
bw.close();
} catch (IOException e) {
e.printStackTrace();
}
return true;
}
That will then run two other threads on the server, one that will run the scan itself and wait for it to finish so that it can get the final scan data. And the other which constantly updates the output from the std error stream which is then polled at intervals from the clients browser. This is much like showing the ongoing output from the terminal.
The scan thread (which fails to start the process) [EDIT 1]:
private static class ScanThread extends Thread {
private String cc, sc;
public ScanThread(String country_code, String satellite_code) {
cc = country_code;
sc = satellite_code;
}
public void run() {
ProcessBuilder pb = new ProcessBuilder("/usr/bin/w_scan",
"-fs", "-c" + cc, "-s" + sc);
pb.redirectOutput(new File(satellite_scan_file));
Process process;
try {
System.out.println("Scan thread started");
process = pb.start();
IOScanErrorOutputHandler error_output_handler = new IOScanErrorOutputHandler(process.getErrorStream());
error_output_handler.start();
int result = process.waitFor();
System.out.println(cc + " - " + sc + " - " +
"Process.waitFor() result " + result);
} catch (IOException e) {
System.out.println(e.getMessage());
e.printStackTrace();
} catch (InterruptedException e) {
System.out.println(e.getMessage());
e.printStackTrace();
}
System.out.println("Scan thread finished");
}
}
The error output stream thread which captures the output which obviously doesn't start due to the scan thread failing:
private static class IOScanErrorOutputHandler extends Thread {
private InputStream inputStream;
IOScanErrorOutputHandler(InputStream inputStream) {
this.inputStream = inputStream;
}
public void run() {
Scanner br = null;
try {
System.out.println("Scan thread Error IO capture running");
br = new Scanner(new InputStreamReader(inputStream));
String line = null;
while (br.hasNextLine()) {
line = br.nextLine();
scan_error_output.append(line + System.getProperty("line.separator"));
}
} finally {
br.close();
}
System.out.println("Scan thread Error IO capture finished");
scan_error_output = null;
}
}
And the server function which returns the std error output progress:
#Override
public String pollScanResult(String user) {
if (validateUserEdit(user) == null) return null;
StringBuilder sb = scan_error_output; // grab instance
if (sb == null) return null;
return sb.toString();
}
As mentioned above, Runtime.exec() works fine, but the ProcessBuilder is failing.
NB: I'm on Linux Mint 18.1, using Apache Tomcat 8 as the server, linux default JDK 8 and GWT 2.7 [Correction from 2.8] in Eclipse Neon.
Can anyone see what I am doing wrong?
Many thanks in advance...
[EDIT 1]
Whilst developing this on another machine, Linux Mint 17.2, JDK 8 and Apache Tomcat 7, for DVB-T, this method worked fine and polling for the scan output showed up in the client's browser.
The ProcessBuilder.start still returns 1 and an empty file is created for the output scan file.
[EDIT 2]
It appears that the reason the ProcessBuilder is failing is because the user 'tomcat8' doesn't have permissions to run 'w_scan'. 'w_scan' works from the terminal, but not from the tomcat server. Somehow I've got to fix that now.
[SOLUTIONS]
After being put in the right direction by VGR for getting the error stream from the ProcessBuilder, I started digging further and found I was getting:
main:3909: FATAL: failed to open '/dev/dvb/adapter0/frontend0': 13 Permission denied
Apache tomcat 8 didn't have permission to access the DVB-S frontend to run a scan. This was fixed in two ways:
1 - 03catalina.policy I added the extra permissions (whether they made a difference I do not know).
grant codeBase "file:/dev/dvb/-" {
permission java.io.FilePermission "file:/dev/dvb/-", "read, write";
permission java.security.AllPermission;
};
2 - The dvb frontends belong to the 'video' group. So I needed to add the user tomcat8 to that group.
usermod -a -G video tomcat8
All works for now...

You are not doing the same thing with ProcessBuilder that you’re doing with Runtime.exec, so I don't know why you think ProcessBuilder is the problem.
You have a few problems with how you’re writing the command’s output to a file.
First, the presence of ">", satellite_scan_temp_file in your ProcessBuilder command is incorrect. Output redirection is not part of any command; it is handled by a shell. But when you run with Runtime.exec or ProcessBuilder, you are not running in a shell, you are executing the process directly. Neither w_scan nor any other command considers > a special character.
The correct way to redirect to a file is with the redirectOutput method:
ProcessBuilder pb = new ProcessBuilder(
"/usr/bin/w_scan", "-fs", "-s" + satellite_code, "-c" + country_code);
pb.redirectOutput(new File(satellite_scan_temp_file));
Second, your ScanThread code is ignoring the (currently incorrect) redirect, and is attempting to read the command’s output. But there is no output, because you are redirecting it all to a file.
Once you are properly redirecting output to a file, you can remove your BufferedReader and BufferedWriter loops completely.
Finally, it is worth noting that the error output you captured probably told you that > is not a valid argument to the w_scan process.

execute julia scripts from Java

I'm coding Julia script with ZeroMQ.
My goal is to communicate with ZMQ between two scripts. Here is an example:
# script1
using ZMQ
ctx = ZMQ.Context()
sockDealer = ZMQ.Socket(ctx, DEALER)
ZMQ.set_identity(sockDealer, "idA")
ZMQ.connect(sockDealer, "tcp://localhost:5555")
ZMQ.send(sockDealer, "hello world!")
ZMQ.close(sockDealer)
ZMQ.close(ctx)
#script2
using ZMQ
function pollrecv(socket::ZMQ.Socket,zmsg::Message)
rc = -1
while true
rc = ccall((:zmq_msg_recv, ZMQ.zmq), Cint, (Ptr{Message}, Ptr{Void}, Cint),
&zmsg, socket.data, ZMQ.ZMQ_DONTWAIT)
if rc == -1
# Base.Libc.EAGAIN = 11
# Problem unsolved: Failure to find Base.Libc.EAGAIN
if !(ZMQ.zmq_errno() == 11)
throw(ZMQ.StateError(ZMQ.jl_zmq_error_str()))
end
return false
else
ZMQ.get_events(socket) != 0 && notify(socket)
break
end
end
return true
end
ctx = ZMQ.Context()
sockRouter = ZMQ.Socket(ctx, ROUTER)
ZMQ.bind(sockRouter, "tcp://*:5555")
fini = false
while !fini
println("listening...")
idSock = Message()
while pollrecv(sockRouter, idSock)
msg = ZMQ.recv(sockRouter)
println("msg recv: " * bytestring(msg))
fini = true
end
sleep(1)
end
ZMQ.close(sockRouter)
ZMQ.close(ctx)
I can execute them with Julia on the command prompt. Everything goes fine. Script 2 can receive the message of Script 1.
Now, I need to execute them from Java. Meaning that I need to create a java project which is just like a controller. Here is my Java project:
public class Container {
private Vector<String[]> commands;
public Container() {
this.commands = new Vector<String[]>();
}
public void addCommand(String[] strs) {
this.commands.addElement(strs);
}
public void execute() {
for(int i = 0; i < this.commands.size(); i++) {
try {
Process p = Runtime.getRuntime().exec(this.commands.get(i));
if(p.waitFor() != 0){
System.err.println("exit value = " + p.exitValue());
}
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
StringBuffer stringBuffer = new StringBuffer();
String line = null;
while((line = in.readLine()) != null){
stringBuffer.append(line + "-");
}
System.out.println(stringBuffer.toString());
} catch (IOException ex) {
// TODO Auto-generated catch block
ex.printStackTrace();
} catch(InterruptedException e){
System.err.println(e);
}
}
}
}
//main
public class Main {
public static void main(String[] args) {
Container c = new Container();
String[] script1 = {"/usr/bin/julia", "/home/thomas/Julia/script1.jl"};
String[] script2 = {"/usr/bin/julia", "/home/thomas/Julia/script2.jl"};
c.addCommand(script1);
c.addCommand(script2);
c.execute();
}
}
However, when I run my java project, I can see that it keeps running but I can't see anything on the console: no result, no message, no error.
I think there is something wrong in my java project.

You'll want to run the two scripts concurrently: script2 is the server script, so it should be running when you run script1. As it is now, Process.waitFor() will wait for script1, the client script, to complete, before executing the server script script2 in the next for iteration.
You could start them as such:
String[] clientScript = { "/usr/bin/julia", "/home/thomas/Julia/script1.jl" };
String[] serverScript = { "/usr/bin/julia", "/home/thomas/Julia/script2.jl" };
Process server = Runtime.getRuntime().exec(serverScript);
Process client = Runtime.getRuntime().exec(clientScript);
and instantiate two threads to read their outputs:
(new ProcessReader(server)).start();
(new ProcessReader(client)).start();
using
public class ProcessReader extends Thread {
private Process p;
public ProcessReader(Process p) {
this.p = p;
}
#Override
public void run() {
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
try {
String line;
while ((line = in.readLine()) != null) {
System.out.println("Read: " + line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Although, since the clientScript doesn't produce any output, you could just
start the scripts, and only read the output from the server script - no thread needed.
There's one more thing to consider: the serverScript must be listening... before the clientScript attempts to connect. So you may want to do this:
Process server = Runtime.getRuntime().exec(serverScript);
BufferedReader in = new BufferedReader(new InputStreamReader(server.getInputStream()));
if ( in.readLine().equals("listening...") ) {
Process client = Runtime.getRuntime().exec(clientScript);
String line;
while ( (line=in.readLine()) != null )
System.out.println("Read: " + line );
}

Since this is not a specific answer to your question, this may help to you or other users that attempt to similar jobs.
JuliaCaller is an early stage library for calling Julia from Java. It executes the Julia executable as a Java process and runs a script in the Julia side. This script opens a TCP server that listens on a given port number. Every command, statement or expression sent from Java is then executed and results are sent back to Java in JSON format.
This library also implements the standard javax.script interface, that means, Julia libraries, functions, and programs can run like a scripting language that is implemented in Java (mimics).
Here is the example:
Constants.setProperties(Constants.JULIA_PATH, "/usr/local/bin/julia");
Constants.setProperties(Constants.JULIA_PORT, "8001");
// Creating a scripting interface for Julia
manager = new ScriptEngineManager();
engine = manager.getEngineByName("Julia");
// Sending command 'a = 3' to Julia from Java
engine.eval("a = 3");
// Handling the result in Java
Object a = engine.get("a");
More examples are given in the GitHub page.
Source code with Apache License

Execution of Program from Program with Time Constraints (Java)

I'm trying to make program which runs some executable program(call it p), given time limit t ms. It does following tasks:
If program p has executed normally, print it's output to console.
If program p couldn't execute completely within time limit, print "Sorry, needs more time!" and then terminate execution of p.
If program p has terminated abnormally (e.g. RuntimeError), print "Can I've some debugger?"
I'm using ProcessResultReader class in the following program from here. My program is working as long as p finishes it's execution normally or terminate abnormally. But, it doesn't terminate if p itself doesn't terminate after timeout.(Try p with simple while(true) loop with no exit condition). It seems that thread stdout is alive even after execution of stdout.stop(). What am I doing wrong in this code?
Thanks.
import java.util.concurrent.TimeUnit;
import java.io.*;
class ProcessResultReader extends Thread
{
final InputStream is;
final StringBuilder sb;
ProcessResultReader(final InputStream is)
{
this.is = is;
this.sb = new StringBuilder();
}
public void run()
{
try
{
final InputStreamReader isr = new InputStreamReader(is);
final BufferedReader br = new BufferedReader(isr);
String line = null;
while ((line = br.readLine()) != null)
{
this.sb.append(line).append("\n");
}
}
catch (final IOException ioe)
{
System.err.println(ioe.getMessage());
throw new RuntimeException(ioe);
}
}
#Override
public String toString()
{
return this.sb.toString();
}
public static void main(String[] args) throws Exception
{
int t = 1000;
Process p = Runtime.getRuntime().exec(cmd); //cmd is command to execute program p
ProcessResultReader stdout = new ProcessResultReader(p.getInputStream());
stdout.start();
if(!p.waitFor(t, TimeUnit.MILLISECONDS))
{
stdout.stop();
p.destroy();
System.out.println("Sorry, needs more time!");
}
else
{
if(p.exitValue()==0) System.out.println(stdout.toString());
else System.out.println("Can I've some debugger?");
}
}
}

According to java docs,
stdout.stop() was deprecated and even stdout.destroy() is never implemented.
For more information, see Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
you could try this instead.
String cmd="cmd /c sleep 5";
int timeout = 1;
Process p = Runtime.getRuntime().exec(cmd); //cmd is command to execute program p
ProcessResultReader stdout = new ProcessResultReader(p.getInputStream());
stdout.start();
if(!p.waitFor(timeout, TimeUnit.MILLISECONDS))
{
stdout.stop();
p.destroy();
System.out.println("Sorry, needs more time!");
System.out.flush();
}
else
{
if(p.exitValue()==0) System.out.println(stdout.toString());
else System.out.println("Can I've some debugger?");
}

How to run a bat by java and can stop it when time out?

I need a function whose argument is bat's fileName and a float means timeOut. I've used Process in java to do it. But if I want to stop it, I find the p.destroy() cannot stop the exe file which be called by bat file and still runs.So ,how can I stop it like "Ctrl"+"C" in cmd?
public void exec(String path, float timeOutFloat) throws IOException, InterruptedException {
Runtime r = Runtime.getRuntime();
Process p = r.exec(new String[] { path });
ThreadReadExec2 thread = new ThreadReadExec2(p.getInputStream());
thread.start();
long timeOut = (long) ((float) timeOutFloat) * 1000;
long time = 0;
long onceTime = 100;
while (thread.isAlive()) {
Thread.sleep(onceTime);
time += onceTime;
if (time > timeOut) {
p.destroy();
Thread.sleep(onceTime);
}
}
int res = p.waitFor();
System.out.println("res:" + res);
}
class ThreadReadExec2 extends Thread {
InputStream input;
public ThreadReadExec2(InputStream input) {
this.input = input;
}
#Override
public void run() {
BufferedReader ir = new BufferedReader(new InputStreamReader(input));
try {
String line;
while ((line = ir.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
}
}
}

The reason that this is happening is likely because the destroy method is killing the command shell you invoked via the batch file, but not the process that that batch file in turn invoked.
You essentially need to kill the process tree of the batch file.
There are some methods in this question that suggest ways to accomplish this in Java, although it's somewhat roundabout (link to the one that seems the most promising):
https://stackoverflow.com/a/7627648/3583500

How to use java program to run command prompt commands?

this is my first time posting here, so I'm not really sure what to say/ask.
Anyways, I am trying to make a simple java program that runs command prompt commands from the java program, mainly used for ping flood (ping flooding myself).
Here is my current code
public class Core extends JFrame {
JTextField ipTextField;
int packets = 0;
boolean running = false;
public Core() {
super("Fatique");
Container container = getContentPane();
JButton bAttack = new JButton("Start Attack");
JButton bStop = new JButton("Stop Attack");
JPanel jPanel = new JPanel();
container.setLayout(new FlowLayout());
ipTextField = new JTextField("IP Address", 30);
container.add(ipTextField);
bAttack.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
String input = ipTextField.getText();
String[] value = input.split(":");
int amountOfPackets = Integer.parseInt(value[1]);
exec("cmd /c" + input + " -t -n " + amountOfPackets);
running = true;
}
});
bStop.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
stop();
}
});
if(!running) {
jPanel.add(bAttack);
} else {
jPanel.add(bStop);
}
add(jPanel);
}
public void exec(String cmd) {
try {
Process p = Runtime.getRuntime().exec(cmd);
System.out.println(getOutput(p) + " - " + getPacketsSent());
} catch (IOException e) {
e.printStackTrace();
}
}
public String getOutput(Process p) {
String output = null;
try {
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = null;
while ((line = in.readLine()) != null) {
output = line;
packets++;
}
return output;
} catch (IOException e) {
System.err.println(e.getStackTrace());
}
return null;
}
public int getPacketsSent() {
return packets;
}
public void stop() {
exec("cmd /c break");
running = false;
}
public static void main(String[] args) {
Core c = new Core();
c.setSize(500, 300);
c.setVisible(true);
c.setResizable(false);
c.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
c.setLocationRelativeTo(null);
}
I'm quite new at java, so that might not do what I want it to do.
What I want it to do is I enter an ip address in the textfield, and split it with ":", and after that the amount of packets, for instance
127.0.0.1:100
Though now when I try to use that ip and packet amount, it returns "null - 0" (from exec method), and I'm not even sure if it did anything related to ping.
What I am trying to accomplish is as I already said, ping flood myself, and then output whatever I get as response, though I have no idea if this code does anything even related to that, I mostly use logic when coding java.
public String getOutput(Process p) {
String output = null;
try {
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = null;
while ((line = in.readLine()) != null) {
output = line;
packets++;
}
return output;
} catch (IOException e) {
System.err.println(e.getStackTrace());
}
return null;
}
Could someone explain me why my code code is not working how I want it to work? Please don't judge, as I already said, I'm quite new to java programming.
EDIT: Here is a quick "informative" explanation of what I am trying to accomplish.
I type in an ip address and how many packets I want to send. In this explanation, I am using localhost ip, and 5 packets.
I start the attack. At this part, I want the program to run cmd prompt command
ping 127.0.0.1 -t -n 5
127.0.0.1 being the ip that I put in the textfield in my program, and 5 is the amount of packets I put in the textfield.
I started the attack, so this is what should happen in the command prompt:
The language is Finnish, but still the same thing.
This is the basic explanation of what I am trying to accomplish, hopefully someone understood and can help/tell why my code is not working, or is working but not printing the proper lines in eclipse console.

There is a problem with your getOutput method. It looks like you intend to collect every line of output. But in fact, since you are assigning line to output, you will only return the last line before the end of stream.
To fix this, change
output = line;
to
output += line + "\n";
Or to be more correct:
output += line + LINE_SEPARATOR;
where you previously declared the latter as:
final String LINE_SEPARATOR = System.getProperty("line.separator");
That doesn't directly explain why you are getting null, but that might be because the command you are running is writing output to the 'error' stream rather than the 'output' stream.

Try something like this:
try {
Runtime rt = Runtime.getRuntime();
Process p = rt.exec("ping 192.168.16.67");
InputStream in = p.getInputStream();
OutputStream out = p.getOutputStream ();
InputStream err = p.getErrorStream();
p.destroy();
} catch(Exception exc) {}
Then, you'll have to read the out variable to parse the ping command output continuously.

bAttack.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
String input = ipTextField.getText();
String[] value = input.split(":");
int amountOfPackets = Integer.parseInt(value[1]);
try {
p=Runtime.getRuntime().exec("ping -n "+amountOfPackets+" "+value[0]);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
running = true;
}
Just a small modification of your code. get output is as:
public String getOutput(Process p) {
String output = null;
try {
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = null;
while ((line = in.readLine()) != null) {
output =output+ line+"\n";
packets++;
}
return output;
} catch (IOException e) {
System.err.println(e.getStackTrace());
}
return null;
}
Here output is JTextArea I have taken to display the output of PING process. I cannot show you the output because I lack reputation.
I don't know why first line is null. Anyway, it works.
Hope this help you. Have good time coding.