Launching external console application from Java

Question

Hi

in a Java application I need to run an external console application. With the window's ones everything is OK:

try {
System.out.println("Running...");
    Runtime.getRuntime().exec("notepad.exe");
    System.out.println("End.");
}
catch(Exception e) {
    System.out.println(e.getMessage());
}

launches notepad successfully.

But if I put D:\\MyProg.exe or .bat or even cmd.exe (which is it PATH as notepad is) it does not work. Without any exeptions. Just:

Running...
End.

Can somebody help? Thanx.

Answer 1

It is because notepad placed in special folder and this folder exists in Path variable.

Run cmd using following line:

Runtime.getRuntime().exec("cmd.exe /c start");

Run other application:

Runtime.getRuntime().exec("cmd.exe /c start C:\\path\\to\\app.exe");

Answer 2

First off, most likely Runtime.exec() is returning asynchronously, so just printing "end" will always work, since the exec call returns immediately, which is what you're seeing.

There's a bunch of other problems that could be showing up here. I think what is happening is that the programs you are calling might be outputting I/O on stdout that you are failing to read, or perhaps you need to wait for it to finish before exiting the java process. There's a great article on the various problems with Runtime.exec() you should probably read, it covers this and other problems.