Question

There’s plenty of information on running Java apps as services, but I need to know how to detect whether a windows service is running or not. Does anyone know how???

At the DOS prompt, I can run:

tasklist /svc|findstr "NonRunningService"
echo Return code for N onRunningService is %ERRORLEVEL%
tasklist /svc|findstr "RunningService"
echo Return code for RunningService is %ERRORLEVEL%

I get the following:

Return code for NonRunningService is 1
Return code for RunningService is 0

In code, I have:

int retCode = Runtime.getRuntime.exec("tasklist /svc|findstr \"NonRunningService\"").waitFor();
System.out.println("Return code for NonRunningService is " + retCode);
retCode = Runtime.getRuntime.exec("tasklist /svc|findstr \"RunningService\"").waitFor();
System.out.println("Return code for RunningService is " + retCode);

I get the following output

Return code for NonRunningService is 1
Return code for RunningService is 1

According to the JavaDocs, the waitFor() should block until the process finishes, and give me the exit value of the process.

I’ve also tried using the Process/ProcessBuilder command line calls:

//'tasklist /nh /fi "SERVICES eq RunningService"' will return a line for 
// each running service of the requested type.
Process p1 = new ProcessBuilder("tasklist", "/nh", "/fi" "SERVICES eq RunningService").start();
p1.waitFor();
BufferedReader is = new BufferedReader(new InputStreamReader(p1.getInputStream()));
String line = is.readLine();
System.out.println("Service - " + line);
System.out.println("Running? ", (line==null?"No":"Yes");

gives:

Service -
Running? No

even when I get lines in the output at the command line!

Answer 1

I recreated your code and added some extra debugging output by creating a class to print the output from process:

private static class Writer implements Runnable {

    private InputStream is;

    public Writer(InputStream is) {
        this.is = is;
    }

    @Override
    public void run() {
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(is));
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
}

In the main method I then started an instance of this before calling waitFor():

public static void main(String[] args) throws Exception {
    String command = "tasklist /svc | findstr \"svchost.exe\"";
    Process p = Runtime.getRuntime().exec(command);

    new Thread(new Writer(p.getInputStream())).start();
    new Thread(new Writer(p.getErrorStream())).start();

    System.out.println("Return code: " + p.waitFor());

}

The output from this is:

ERROR: Invalid argument/option - '|'.
Type "TASKLIST /?" for usage.

Because the command isn’t executed in a shell, you first need to call the Windows shell, and pass in the command as an argument:

String command = "cmd /c tasklist /svc | findstr \"svchost.exe\"";

After changing this the output is now Return code: 0.

I’ve found a strange issue however, in that if you don’t handle the output from the process’s stdout channel, for some reason the process does not terminate. To get around this, I’ve had to put in a loop to read and discard the output from the process:

public static void main(String[] args) throws Exception {
    String command = "cmd /c tasklist /svc | findstr \"svchost.exe\"";
    Process p = Runtime.getRuntime().exec(command);
    while(p.getInputStream().read() != -1) {} //hangs without this line

    System.out.println("Return code: " + p.waitFor());

}