Executing in java code an external program that takes arguments

Question

Process p;
String line;
String path;
String[] params = new String [3];

                    params[0] = "D:\\prog.exe";
        params[1] = picA+".jpg";
        params[2] = picB+".jpg";

        try {
            p = Runtime.getRuntime().exec(params);

            BufferedReader input =
                new BufferedReader
                  (new InputStreamReader(p.getInputStream()));

              while ((line = input.readLine()) != null)
                  System.out.println(line);


              input.close();
        } catch (IOException e) {System.out.println(" procccess not read"+e);}

i don't get any error, just nothing

in cmd.exe prog.exe is working fine

What to improve in order to make this code working?

Answer 1

Use a p = new ProcessBuilder(params).start(); instead of

p = Runtime.getRuntime().exec(params);

Other than that looks fine.

Answer 2

Perhaps you should use waitFor() to obtain the result code. This means that the dump of the standard output must be done in another thread:

String path;
String[] params = new String [3];

                    params[0] = "D:\\prog.exe";
        params[1] = picA+".jpg";
        params[2] = picB+".jpg";

        try {
            final Process p = Runtime.getRuntime().exec(params);
            Thread thread = new Tread() {
                public void run() {
                    String line;
                    BufferedReader input =
                       new BufferedReader
                         (new InputStreamReader(p.getInputStream()));

                     while ((line = input.readLine()) != null)
                         System.out.println(line);


                     input.close();
               } catch (IOException e) {System.out.println(" procccess not read"+e);}
            };
            thread.start();
            int result = p.waitFor();
            thread.join();
            if (result != 0) {
                System.out.println("Process failed with status: " + result);
            }

Answer 3

I just tried this on my system:

public static void main(String[] args) throws IOException {
        String[] params = { "svn", "help" };
        Process p = Runtime.getRuntime().exec(params);

        BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));

        String line;
        while ((line = input.readLine()) != null) {
            System.out.println(line);
        }

        input.close();
    }

and it worked fine. Are you sure the program you're using actually prints something to the console? I see it takes jpegs as input, maybe it writes to a file, not stdout.