Execute a CMD file stored in a JARTag(s): IO


In this example, a CMD file is stored a JAR file. The Java code extracts the file as a ressource, launch a Windows CMD Shell and write the content to the stdin without any temporary file.

In this How-to, the CMD included is used to trigger the default Windows screen saver.

scrnsave.scr /s

import java.io.*;

public class StartScreenSaver {
  public static void main(String args[]) throws IOException {
    new StartScreenSaver().doit();
  }
  
  public void doit() throws IOException{
    String line;
    OutputStream stdin = null;
    InputStream stderr = null;
    InputStream stdout = null;
    
    try {
      // that our CMD file in our JAR
      InputStream is = 
        getClass().getResource("/screensaver.cmd").openStream();
      BufferedReader brCmdLine = 
        new BufferedReader(new InputStreamReader(is));
      
      // launch CMD and grab stdin/stdout and stderr
      Process process = Runtime.getRuntime ().exec ("cmd");
      stdin = process.getOutputStream ();
      stderr = process.getErrorStream ();
      stdout = process.getInputStream ();
  
      // "write" the CMD file into stdin
      while ((line = brCmdLine.readLine()) != null) {
        line += "\n";
        stdin.write(line.getBytes() );
      }
      stdin.flush();
      stdin.close();
      
      // clean up if any output in stdout
      BufferedReader brCleanUp = 
        new BufferedReader (new InputStreamReader (stdout));
      while ((line = brCleanUp.readLine ()) != null) {
        //System.out.println ("[Stdout] " + line);
      }
      brCleanUp.close();
      
      // clean up if any output in stderr
      brCleanUp = 
        new BufferedReader (new InputStreamReader (stderr));
      while ((line = brCleanUp.readLine ()) != null) {
        //System.out.println ("[Stderr] " + line);
      }
      brCleanUp.close();
    }
    catch (IOException e) {
      e.printStackTrace();
    }
    finally {
      stdout.close();
      stderr.close();
    }
  }
}

Get the JAR here.


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