Develop Reference

Get a list of active programs in java

I need to retrieve a list of currently open programs using java. The following code gives me a list of all the programs that are active including any background processes however I need only a list of active programs.
try {
String line;
Process p = Runtime.getRuntime().exec(System.getenv("windir") +"\\system32\\"+"tasklist.exe");
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((line = input.readLine()) != null) {
System.out.println(line);
}
input.close();
} catch (Exception err) {
err.printStackTrace();
}
I am not going to be aware what programs are currently open and so will not be able to find it by searching for a series of names, as I have seen some people recommend this method.
By active program I am meaning any program that is available to the user to interact with through a window. The task manager window already splits the programs(in detailed view) into apps and background processes and I would like to be able to retrieve any programs that would be sorted under the apps section.

add this command line
String command="powershell -command \"get-Process cmd | format-table mainwindowtitle\"";
and use it here
Process p = Runtime.getRuntime().exec(command);

You can use the windows cmd like this :
try {
String process;
// getRuntime: Returns the runtime object associated with the current Java application.
// exec: Executes the specified string command in a separate process.
Process p = Runtime.getRuntime().exec(System.getenv("windir") +"\\system32\\"+"tasklist.exe /fo csv /nh");
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((process = input.readLine()) != null) {
System.out.println(process); // <-- Print all Process here line
// by line
}
input.close();
} catch (Exception err) {
err.printStackTrace();
}

Shell command not executed

I have a weird problem when trying to execute a shell command from within a java program. Since there exist thousands of websites that explain how to do it I used the following recommended code:
public String executeShellCommand (String command)
{
try
{
StringBuffer sb = new StringBuffer();
String line = "";
Process p = Runtime.getRuntime().exec(command);
BufferedReader reader = new BufferedReader(new InputStreamReader(
p.getInputStream()));
while ((line = reader.readLine()) != null)
sb.append(line + "\n");
p.waitFor();
return sb.toString();
}
catch (Exception e)
{
e.printStackTrace();
}
return null;
}
Acutally, when I try to execute for instance ls -aF is works fine and I get some output as a result. Therefore I'm pretty sure that the above code is, in principal, correct. However, I got another program I'd like to run and that produces a file as an output. I would like to execute it the above way but it never is executed and no output file is generated. Also I do not get any error, warnings or whatsoever in java. When copy and pasting the actual command argument string into the console the execution of the programm/command directly in the shell works fine and the output file is generated. So the command I pass to the method is also correct.
Are there additional things I need to pay attention to when trying to execute a shell command from within java?
UPDATE: I modified my code according to the suggestions. However, it is still hanging:
public String executeShellCommand(List<String> command, String logfile, boolean waitForProcess) { try {
ProcessBuilder pb = new ProcessBuilder(command);
System.out.println("pb.toString() = " + pb.toString());
Process p = pb.start();
System.out.println("2");
BufferedReader err = new BufferedReader(new InputStreamReader(p.getErrorStream()));
BufferedReader out = new BufferedReader(new InputStreamReader(p.getInputStream()));
System.out.println("3");
StringBuilder errSb = new StringBuilder();
StringBuilder outSb = new StringBuilder();
String line;
System.out.println("4");
while ((line = err.readLine()) != null) { // <--- code hangs here
errSb.append(line + "\n");
System.out.println("errSb = " + errSb.toString());
}
System.out.println("4a");
while ((line = out.readLine()) != null) {
outSb.append(line + "\n");
System.out.println("outSb = " + outSb.toString());
}
System.out.println("5");
if(waitForProcess) {
System.out.println("Wait for process");
p.waitFor();
} else {
System.out.println("Sleep 5000");
Thread.sleep(5000);
}
System.out.println("6");
//Log result to file
if(logfile != null) {
OutputStreamWriter outWriter = new OutputStreamWriter(new FileOutputStream(logfile));
outWriter.write(errSb.toString());
outWriter.close();
}
return errSb.toString();
} catch(Exception e) { e.printStackTrace(); } return null; }

This will block if your command writes too many characters to stderr. Like for sdtout, Java redirect stderr through a pipe, and if you do not read the pipe, it can fill up and block (size of the pipe is probably less than 256 bytes). To avoid that, you need to read from the Process.getErrorStream(), preferable from another thread as the main thread is busy reading from the Process.getInputStream().
A simpler way to avoid that is to use the ProcessBuilder class instead of Runtime.exec() and ProcessBuilder.redirectErrorStream(true) so that both stdout and stderr are merged into the Process.getInputStream()

As per Process javadoc :
Because some native platforms only provide limited buffer size for standard input and output streams, failure to promptly write the input stream or read the output stream of the subprocess may cause the subprocess to block, or even deadlock.
You are calling p.waitFor(). If we carefully read the waitFor() documentation:
Causes the current thread to wait, if necessary, until the process represented by this Process object has terminated.
You are waiting for a process which hangs, because its error stream and output stream are never read.
What you should do, is to read these streams:
p.start();
BufferedReader err= new BufferedReader(new InputStreamReader(p.getErrorStream()));
BufferedReader out = new BufferedReader(new InputStreamReader(p.getOutputStream()));
StringBuilder errSb = new StringBuilder();
StringBuilder outSb = new Stringbuilder();
String line;
while ((line = err.readLine()) != null) {
errSb.append(line);
}
while ((line = out.readLine()) != null) {
outSB.append(line);
}
int retCode = p.waitFor(); //0 for success
System.out.println(retCode);
System.err.println(errSB.toString());
You should always read the error stream when calling external programs via the Process class, else you may find yourself in this odd situation where a process hangs forever. (well until someone else -the operating system, another application, etc- kills it, more exactly).
I've also noticed that you use the Runtime.getRuntime() which is not the recommended way to run external programs, starting with java 1.5, as per javadoc:
As of 1.5, ProcessBuilder.start() is the preferred way to create a Process.
ProcessBuilder pb = new ProcessBuilder("ls" , "-aF");
Process p = pb.start();

capture output from c++ in java without returning

i'm working on java SWING to make GUI for c++ programming . i need the c++ program to be executed in a loop without returning to the java. During this loop i want to capture some output without stepping through
return 0; in c++ program
can i capture output from the c++ file without returning to the java GUI ??
this is my out and in process in my code
try {
int out = 0;
String line;
OutputStream stdin = null;
InputStream stderr = null;
InputStream stdout = null;
// calling the exe file
Process process = new ProcessBuilder("unpattern.exe").start();
stdin = process.getOutputStream();
stderr = process.getErrorStream();
stdout = process.getInputStream();
// input process
// "write" the parms into stdin
line = "1";
stdin.write(line.getBytes());
stdin.flush();
//line = "tx.getText()" + "\n";
// stdin.write(line.getBytes());
// stdin.flush();
stdin.close();
// output process
// clean up if any output in stdout
BufferedReader brCleanUp =
new BufferedReader(new InputStreamReader(stdout));
while ((line = brCleanUp.readLine()) != null) {
// counter of the defects
System.out.println(line);
} catch (IOException ex) {
Logger.getLogger(QeyeGui3.class.getName()).log(Level.SEVERE, null, ex);
}

Your while loop is missing its closing brace:
// ....
while ((line = brCleanUp.readLine()) != null) {
// counter of the defects
System.out.println(line);
// **** it should go here
}
I suggest you continuously get the text that is passed into the BufferedReader in your while loop. If you are doing this within a Swing application's SwingWorker, then you could use the publish/process method pair to update the Swing GUI with the information that is transmitted.

i could to find a suitable solution for my problem in this link
Capture the output of DOS (command prompt) and display in a JAVA Frame
i added the buffer in string builder so i could make it :)
thank you for every help :)

How to edit file on console from Java?

I'm trying to edit a file from CLI. I'm executing the nano command (I know that command will always be available); when I execute it, I can see nano's output but I cannot interact with it. How can I pass user input to the command? Do you have a better idea to easily edit a file from within my Java app?
This is my code:
String command = "nano /tmp/163377867.txt ";
try {
Process process = Runtime.getRuntime().exec(command);
InputStream inputStream = process.getInputStream();
InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String line;
while ((line = bufferedReader.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}

The problem with Java's Runtime.exec is that it connects stdin and stdout to "pipes," while many console programs need a TTY device.
One way to solve this problem is to make the Java program's controlling terminal available to the program you execute:
Process proc = Runtime.getRuntime().exec(new String[]{
"sh", "-c", command+" </dev/tty >/dev/tty"});
proc.waitFor(); // wait for user to finish editing the file

Communicating with C++ process from Java

First, I saw a few Q's about this issue in the site, but didn't see any answer that solve my problem.
I have a program written in Java and it calls a cmd program written in C++. (this is an assumption since I don't have the actual source) I know the expected I/O of the C++ program, in the cmd it is two lines of output and then it waits for string input.
I know that the first output line of the program is through error stream, and I receive it properly (this is expected), but I don't get the second line in error or input stream.
I tried to write to the program right after the first line ( the error line) and didn't got stuck, but there was no response.
I tried using 3 different threads, for each stream, but again, nothing was received in input/error stream after the first line, and the program didn't respond to writing through output stream.
My initializers are:
Process p = Runtime.getRuntime().exec("c:\\my_prog.exe");
BufferedReader err = new BufferedReader(new InputStreamReader(p.getErrorStream()));
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
BufferedWriter output = new BufferedWriter(new OutputStreamWriter(p.getOutputStream()));
Is it possible at all or maybe it depends on the C++ program?
Thanks,
Binyamin

If you want to call native applications like C and C++ from Java, you need to use JNI.

I would suggest to put the input in the program when it has started, it will propably use that as input when it wants it.

Here is how I execute any command line in Java. This command line may execute any program:
private String executionCommandLine(final String cmd) {
StringBuilder returnContent = new StringBuilder();
Process pr;
try {
Runtime rt = Runtime.getRuntime();
pr = rt.exec(cmd);
BufferedReader input = new BufferedReader(new InputStreamReader(pr.getInputStream()));
String line = null;
while ((line = input.readLine()) != null) {
returnContent.append(line);
}
input.close();
LOG.debug(returnContent.toString());
// return the exit code
pr.waitFor();
} catch (IOException e) {
LOG.error(e.getMessage());
returnContent = new StringBuilder();
} catch (InterruptedException e) {
LOG.error(e.getMessage());
returnContent = new StringBuilder();
}
return returnContent.toString();
}