Problem executing .exe file created with C++ code

[Singing Boyo]

Hi there all.

I have recently started trying to gain some experience with C++ code, but I also wanted to expand my Java experience, so I tried created a Java program that would execute the C++ .exe file for the C++ program. The C++ program started fine, but the console that shows up by just double-clicking the .exe file from within My Computer (I'm running Windows) does not appear, and I then have to go through task manager to end the C++ program, and the Java then ends (using the big red terminate button in Eclipse does not end the C++ program)

I'm wondering if anyone knows a better way to execute the program than what I am using... (Runtime.getRuntime().exec(command)) Maybe I need to change my C++ code, but it works fine with the regular double-click...

Note: The .exe file does contain a line stating that the program does not run through command prompt (double-clicking it in Eclipse showed text... sort-of). I'm not too familiar with Runtime.exec(command), but I believe this may have something to do with it.

Here's my code... the println happens but the C++ console does not appear.

import java.io.IOException;

public class CPPExec {

	public static void main(String[] args){
		try {
			Runtime.getRuntime().exec("ConsoleApplications.exe");
		} catch (IOException e) {
			e.printStackTrace();
		}
		System.out.println("Execution complete");
	}
}

[fxRichard]

I don't fully understand your question but I can tell you one thing you are doing wrong.. try using the following code

public class CPPExec
{
  public static void main(String[] args)
  {
      try
      {
          Process proc = Runtime.getRuntime().exec("ConsoleApplications.exe");
          proc.waitFor();
          System.out.println("Execution complete");
    }catch(Exception e)
    {
         e.printStackTrace();
    }
  }
}

[Singing Boyo]

I'll try to explain my question more fully...

The basic question is... how do you run a C++ program from Java? I managed to execute the .exe file, but the C++ program did not work the same way as it does when run without using the Java code. (No console appeared)

@Richard Thanks for the suggestion. I just can't test it until I get the C++ program running properly.

Note: The line in the .exe file says that it cannot be run in DOS mode, not that it cannot be run through command prompt.

[fxRichard]

Are you running on XP or Vista?

[Singing Boyo]

I'm running on XP

[angryboy]

it should matter if its c++/c or whatever.
have you try making it work w/ notepad first?

try calling it w/:

"cmd /c appName.exe"

"cmd /c start appName.exe"

[Steve11235]

I'm no expert in this area, but I think what AB is getting at is that you won't get a command window without invoking "command" or "cmd" to run the application. Windows does that automatically because it recognizes that it is not a "Windows" program.

I believe the difference in the two commands he lists is that one will wait for the program to complete, while the other will start it in a separate process and go on.

[Singing Boyo]

Thanks angryboy, the cmd /c start worked... now to figure out how to determine when that program exits, and how to run it if I'm using a jar file...

waitFor() just waited for the console to show up...

EDIT: Didn't see steve's post... the cmd /c did not do anything, so cmd /c start is my only option as far as I know

[toadaly]

Double clicking in windows executes javaw, not java. javaw intentionally suppresses console windows to make java apps look like native windows apps.

If you want a console, you can bring one up, and then launch your java app from within it using the 'java' command. You can also create a shortcut that executes 'java' rather than 'javaw', and that will bring up a terminal window too.

[Singing Boyo]

console came up fine with cmd /c start. Now I just need to know when the program exits (get it's return value -- for anyone who doesn't know, C++ returns ints from main methods) and how to run it in a jar file (would I need to have a folder containing all the C++ code as well?)

[Singing Boyo]

Took another look at the Process.waitFor() method and discovered it returns an int... the problem is that it is returned early from my C++ program (returned before the program has exited) I believe this is most likely a problem with the code I am using (Below). Any hints?

My Code:

import java.io.IOException;

public class CPPExec {

	public static void main(String[] args){
		int processExitVal = 0;
		try {
			Process p = Runtime.getRuntime().exec("cmd /c  start ConsoleApplications.exe");
			processExitVal = p.waitFor();
		} catch (IOException e) {
			System.out.println("IOException");
			e.printStackTrace();
		} catch (InterruptedException e) {
			System.out.println("InterruptedException");
			e.printStackTrace();
		}
		System.out.println(processExitVal);
		System.out.println("Execution complete");
	}
}

The System.out.println calls print before my C++ program has exited, and processExitVal is always 0 (even when I make the C++ code return a different value). All and any help is welcome!

[fxRichard]

You need to do this...

     Process p = Runtime.getRuntime().exec("cmd /c  start ConsoleApplications.exe");
     p.waitFor();
     processExitValue = p.exitValue();

If you'r C++ app is printing stuff out to the command line then you need to grab the InputStream via p.getInputStream(); to read the data from the command line.

[Steve11235]

Back to what I was saying before... I *believe* cmd start app.exe starts the app in a separate process, so control immediately returns to cmd, which then terminates. Therefore, everything is doing what it is supposed to. Try removing the "start" and see what happens. I *believe* this will cause cmd to wait until app completes.

@Toadaly- You're right about what you said about java and javaw. I was talking about cmd...

As far as running from a JAR, it doesn't make any difference, as long as app.exe is not in the JAR.

[Singing Boyo]

@Richard I want a separate command line for the C++ program, and I have that, but my code does not wait for the C++ program to exit, despite using waitFor().

@Steve cmd /c app.exe does not work... no command line window shows up.

Tried to find C++ execution commands for the command prompt, but couldn't find anything. If anyone knows some, post them and I'll give them a try.

Thanks for all the help so far,
Singing Boyo

[Steve11235]

Actually, that makes sense. Without start, you are not starting a new process, and the current process does not have a window.

With start, the process you are monitoring is the one that starts another, so it ends almost immediately.

Try using "start" directly and monitoring that process. That might work.

[angryboy]

cmd /? > c:\info.txt && notepad c:\info.txt

its loooong...

[Singing Boyo]

Still no luck with one that creates a command prompt window and exits at the right time, though just using exec("MyApp.exe) returns the correct exit code as far as I can tell. I may just need to make it so that my C++ code starts a new console... or figure out how to create a new command prompt console with Java and make it handle the C++ program.

EDIT: Didn't see AB's post... What???

[Steve11235]

AB told you how to put the cmd help into a file and then open the file with notepad.

Did you try "start" by itself?

[Singing Boyo]

if you meant cmd start myApp.exe or just plain start myApp.exe neither worked... the first one just started a command prompt that never showed up, the second one gave me an error...

[Steve11235]

Yes, that makes sense, now that you told me the result. "start" has to be run from the command line or in a batch file...

I think AB's original idea was the best, but Windows apparently doesn't like it. I think you are running into a limitation of Windows.