Strange issue while running batch file with process builder in java

Question

I have the following java code snippet which runs a batch file( renames a file depending on a flag ). This code works properly. But when i comment the line while( isRunning(p) ) {} then it doesn't work. Can anyone give any reason for that ?

public static void main(String[] args) throws IOException, InterruptedException {
        ProcessBuilder pb = new ProcessBuilder(  fileManipulatorScriptLocation, "Rename_File", "a.txt", "b.txt" );
        pb.directory( new File(targetDirectory) );
        Process p = pb.start();
        while( isRunning(p) ) {}
    }

    public static boolean isRunning(Process process) {
        try {
            process.exitValue();
            return false;
        } catch (IllegalThreadStateException e) {
            return true;
        }
    }

Else the Java process will be ended, because the main method has been finished, along with its child processes. — 11684
– 11684, Commented Jan 16, 2013 at 21:40

Marko Topolnik · Accepted Answer · 2013-01-16 21:40:23Z

4

Instead of the busy-waiting infinite loop, use Process#waitFor. Why it doesn't work: your parent process (Java) dies immediately, dragging the child process with it.

answered Jan 16, 2013 at 21:40

Marko Topolnik

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Archer · Accepted Answer · 2013-01-16 21:45:54Z

0

isRunning() checks for Process#exitValue().

From javadoc:

Returns the exit value for the subprocess.

Returns: the exit value of the subprocess represented by this Process object. by convention, the value 0 indicates normal termination.

Throws: IllegalThreadStateException - if the subprocess represented by this Process object has not yet terminated.

Means, that IllegalThreadStateException is thrown inside isRunning() method if process is still running, but that exceptin is catched, so method return true, otherwise exitValue() return process exist value and isRunning method return false which breaks while loop.

answered Jan 16, 2013 at 21:45

Archer

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