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.

Problems again with child processes in Java

I am on Ubuntu 14.04.
I am trying to run something like ps aux | grep whatevah through Java's class ProcessBuilder. I create two child processes and I make them communicate synchronously, but for some reason, I can not see anything in the terminal.
This is the code:
try {
// What comes out of process1 is our inputStream
Process process1 = new ProcessBuilder("ps", "aux").start();
InputStream is1 = process1.getInputStream();
BufferedReader br1 = new BufferedReader (new InputStreamReader(is1));
// What goes into process2 is our outputStream
Process process2 = new ProcessBuilder("grep", "gedit").start();
OutputStream os = process2.getOutputStream();
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));
// Send the output of process1 to the input of process2
String p1Output = null;
while ((p1Output = br1.readLine()) != null) {
bw.write(p1Output);
System.out.println(p1Output);
}
// Synchronization
int finish = process2.waitFor();
System.out.println(finish);
// What comes out of process2 is our inputStream
InputStream is2 = process2.getInputStream();
BufferedReader br2 = new BufferedReader(new InputStreamReader(is2));
String combOutput = null;
while ((combOutput = br2.readLine()) != null)
System.out.println(combOutput);
os.close();
is1.close();
is2.close();
} catch (IOException e) {
System.out.println("Command execution error: " + e.getMessage());
} catch (Exception e) {
System.out.println("General error: " + e.getMessage());
}
(The System.out.println(p1Output); is just for me to check, the print that has to work is the last one, printing the result of ps aux | grep whatevah.)
I've tried several things, the less silly include:
If I comment everything regarding process2, I get the result of ps aux printed on the terminal
If I run the program as is, it prints nothing to the terminal.
If I uncomment the waitFor call, only ps aux gets printed.
If change the commands to, for example, ls -al and ls -al, then both get printed.
I tried changing "aux" for "aux |" but still nothing is printed.
Closed the buffers, also nothing
etc.
Any help will be sorely appreciated.
Cheers!
EDIT
Minutes after accepting Ryan's amazing answer I made my last try to make this code work. And I succeeded! I changed:
while ((p1Output = br1.readLine()) != null) {
bw.write(p1Output);
System.out.println(p1Output);
}
for:
while ((p1Output = br1.readLine()) != null) {
bw.write(p1Output + "\n");
System.out.println(p1Output);
}
bw.close();
and it works! I remember closing the buffer before, so I don't know what went wrong. Turns out you should not stay awake until late trying to make a piece of code work XD.
Ryan's answer down here is still amazing, though.

Given the advice in the comments, the important thing to note is the necessity to use threads to process input/output for a process in order to achieve what you want.
I've used the link posted by jtahlborn and adapted this solution that you might be able to use.
I created a simple example that will list files in a directory and grep through the output.
This example simulates the command ls -1 | grep some from a directory called test with three files somefile.txt someotherfile.txt and this_other_file.csv
EDIT: The original solution didn't really fully use the "pipe" methodology, as it was waiting fully for p1 to finish before starting p2. Rather, it should start them both, and then the output of the first should be piped to the second. I've updated the solution with a class that accomplishes this.
import java.io.*;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
try {
// construct a process
ProcessBuilder pb1 = new ProcessBuilder("ls", "-1");
// set working directory
pb1.directory(new File("test"));
// start process
final Process process1 = pb1.start();
// get input/error streams
final InputStream p1InStream = process1.getInputStream();
final InputStream p1ErrStream = process1.getErrorStream();
// handle error stream
Thread t1Err = new InputReaderThread(p1ErrStream, "Process 1 Err");
t1Err.start();
// this will print out the data from process 1 (for illustration purposes)
// and redirect it to process 2
Process process2 = new ProcessBuilder("grep", "some").start();
// process 2 streams
final InputStream p2InStream = process2.getInputStream();
final InputStream p2ErrStream = process2.getErrorStream();
final OutputStream p2OutStream = process2.getOutputStream();
// do the same as process 1 for process 2...
Thread t2In = new InputReaderThread(p2InStream, "Process 2 Out");
t2In.start();
Thread t2Err = new InputReaderThread(p2ErrStream, "Process 2 Err");
t2Err.start();
// create a new thread with our pipe class
// pass in the input stream of p1, the output stream of p2, and the name of the input stream
new Thread(new PipeClass(p1InStream, p2OutStream, "Process 1 Out")).start();
// wait for p2 to finish
process2.waitFor();
} catch (IOException e) {
System.out.println("Command execution error: " + e.getMessage());
} catch (Exception e) {
System.out.println("General error: " + e.getMessage());
}
}
}
This is a class that will be used to simulate a process pipe. It uses some loops to copy bytes around, and could be more efficient, depending on your needs, but for the illustration, it should work.
// this class simulates a pipe between two processes
public class PipeClass implements Runnable {
// the input stream
InputStream is;
// the output stream
OutputStream os;
// the name associated with the input stream (for printing purposes only...)
String isName;
// constructor
public PipeClass(InputStream is, OutputStream os, String isName) {
this.is = is;
this.os = os;
this.isName = isName;
}
#Override
public void run() {
try {
// use a byte array output stream so we can clone the data and use it multiple times
ByteArrayOutputStream baos = new ByteArrayOutputStream();
// read the data into the output stream (it has to fit in memory for this to work...)
byte[] buffer = new byte[512]; // Adjust if you want
int bytesRead;
while ((bytesRead = is.read(buffer)) != -1) {
baos.write(buffer, 0, bytesRead);
}
// clone it so we can print it out
InputStream clonedIs1 = new ByteArrayInputStream(baos.toByteArray());
Scanner sc = new Scanner(clonedIs1);
// print the info
while (sc.hasNextLine()) {
System.out.println(this.isName + " >> " + sc.nextLine());
}
// clone again to redirect to the output of the other process
InputStream clonedIs2 = new ByteArrayInputStream(baos.toByteArray());
buffer = new byte[512]; // Adjust if you want
while ((bytesRead = clonedIs2.read(buffer)) != -1) {
// write it out to the output stream
os.write(buffer, 0, bytesRead);
}
}
catch (IOException ex) {
ex.printStackTrace();
}
finally {
try {
// close so the process will finish
is.close();
os.close();
}
catch (Exception ex) {
ex.printStackTrace();
}
}
}
}
This is a class that was created for handling process output, adapted from this reference
// Thread reader class adapted from
// http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html
public class InputReaderThread extends Thread {
// input stream
InputStream is;
// name
String name;
// is there data?
boolean hasData = false;
// data itself
StringBuilder data = new StringBuilder();
// constructor
public InputReaderThread(InputStream is, String name) {
this.is = is;
this.name = name;
}
// set if there's data to read
public synchronized void setHasData(boolean hasData) {
this.hasData = hasData;
}
// data available?
public boolean hasData() { return this.hasData; }
// get the data
public StringBuilder getData() {
setHasData(false); // clear flag
StringBuilder returnData = this.data;
this.data = new StringBuilder();
return returnData;
}
#Override
public void run() {
// input reader
InputStreamReader isr = new InputStreamReader(this.is);
Scanner sc = new Scanner(isr);
// while data remains
while ( sc.hasNextLine() ) {
// print out and append to data
String line = sc.nextLine();
System.out.println(this.name + " >> " + line);
this.data.append(line + "\n");
}
// flag there's data available
setHasData(true);
}
}
The produced output is:
Process 1 Out >> somefile.txt
Process 1 Out >> someotherfile.txt
Process 1 Out >> this_other_file.csv
Process 2 Out >> somefile.txt
Process 2 Out >> someotherfile.txt
To show that piping is really working, changing the command to ps -a | grep usr the output is:
Process 1 Out >> PID PPID PGID WINPID TTY UID STIME COMMAND
Process 1 Out >> I 15016 1 15016 15016 con 400 13:45:59 /usr/bin/grep
Process 1 Out >> 15156 1 15156 15156 con 400 14:21:54 /usr/bin/ps
Process 1 Out >> I 9784 1 9784 9784 con 400 14:21:54 /usr/bin/grep
Process 2 Out >> I 15016 1 15016 15016 con 400 13:45:59 /usr/bin/grep
Process 2 Out >> 15156 1 15156 15156 con 400 14:21:54 /usr/bin/ps
Process 2 Out >> I 9784 1 9784 9784 con 400 14:21:54 /usr/bin/grep
Seeing the grep command in process 2's output shows that the piping is working, with the old solution I posted, this would be missing.
Note the handling of the error stream, which is always good practice, even if you don't plan to use it.
This is a quick and dirty solution that could benefit from some additional thread management techniques, but it should get you what you want.

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.

java: ProcessBuilder makes a memory hog

I have some issues regarding ProcessBuilder.
The program is basically a simple wrapper invoking a command line script.
When running the script on its own via the terminal, the memory consumption stays below 2G.
When running the script via the java wrapper, the memory consumption explodes and even 8G is quickly filled up, resulting in out-of-memory errors.
The code to launch the process is simply:
public static int execute(String command) throws IOException
{
System.out.println("Executing: " + command);
ProcessBuilder pb = new ProcessBuilder(command.split(" +"));
Process p = pb.start();
// display any output in stderr or stdout
StreamConsumer stderr = new StreamConsumer(p.getErrorStream(), "stderr");
StreamConsumer stdout = new StreamConsumer(p.getInputStream(), "stdout");
new Thread(stderr).start();
new Thread(stdout).start();
try {
return p.waitFor();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
The StreamConsumer class is simply a class which consumes the stdout/stderr streams and display them on the console.
...the question is: why on earth does the memory consumption explode?
Regards,
Arnaud
Edit:
Whether I use ProcessBuilder or
Runtime.getRuntime.exec(...), the
result is the same.
The memory bursts tend to appear during unix 'sort' invoked by the
shell script called:
sort big-text-file > big-text-file.sorted
Edit 2 on request of Jim Garrison:
Ok, here is the StreamConsumer class which I omitted because it is rather simple:
class StreamConsumer implements Runnable
{
InputStream stream;
String descr;
StreamConsumer(InputStream stream, String descr) {
this.stream = stream;
this.descr = descr;
}
#Override
public void run()
{
String line;
BufferedReader brCleanUp =
new BufferedReader (new InputStreamReader (stream));
try {
while ((line = brCleanUp.readLine ()) != null)
System.out.println ("[" + descr + "] " + line);
brCleanUp.close();
} catch (IOException e) {
// TODO: handle exception
}
}
}

if you change your command like this :
sort -o big-text-file.sorted big-text-file
is it always the same ?

Maybe its because those StreamConsumer threads are not daemons so they don't die and get garbage collected when your processes return? You could try:
//...
final StreamConsumer stderr = new StreamConsumer(p.getErrorStream(), "stderr");
final StreamConsumer stdout = new StreamConsumer(p.getInputStream(), "stdout");
final Thread stderrThread = new Thread(stderr);
final Thread stdoutThread = new Thread(stdout);
stderrThread.setDaemon(true);
stdoutThread.setDaemon(true);
stderrThread.start();
stdoutThread.start();
//...
Is this behavior happening for single invocation or after doing this many times?