CODEWITHSUNDEEP
javacmdcommand-promptoutput
Woobie
Woobie

Reputation: 113

Getting command prompt output instantly?

Probably a misleading title, but thanks to people on my other question, I got my program somewhat working, though now not sure what to do.

Here is my method to run command prompt commands and return the output

public static String cmdExec(String cmdLine) {
    String line;
    String output = "";
    try {
        Process p = Runtime.getRuntime().exec(cmdLine);
        BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
        while ((line = input.readLine()) != null) {
            output += (line + '\n');
        }            
        input.close();           
        }
    catch (Exception ex) {
        ex.printStackTrace();
    }

    return output;
}

It works how I want it to work, though now when I run this method, it is going to wait until everything is done, and then return the output, which is not what I want.

I made a ping flooding method that uses the cmdExec method. Here is how I call cmdExec()

String[] input = ipTextField.getText().split(":");

    if(input.length == 2) {
        System.out.println(cmdExec("cmd /c ping " + input[0] + " -t -n " + Integer.parseInt(input[1])));

So now for instance, if I type "127.0.0.1:3" in my program, it's going to send 3 packets to localhost. Now the problem here is, instead of printing out the lines I get as output from command prompt 1 by 1, it's going to wait until all the 3 packets are sent, and then print the output full output.

If I type "ping 127.0.0.1 -t -n 3" in command prompt, it's going to print the reply 1 by 1, not all just at once, so how would I go about doing the same in my program?

Upvotes: 3

Views: 3931

Answers (2)

user1131435
user1131435

Reputation:

You can print out continuously with:

while ((line = input.readLine()) != null) {
    System.out.println(line);
    output += (line + '\n');
}

(The following is still useful for future viewers, but is not an applicable answer to the question.) Simply insert a process.waitFor() before reading from the output stream. This command waits until a process dies before continuing. You then don't have to read line by line, either. You can simply dump the buffer all at once.

Either this, or you can find a string which only occurs on the last line (e.g. Minimum in Windows) and change the while condition to:

while((line == input.readline()).indexOf("Minimum") == -1)

Upvotes: 0

Art Vandelay
Art Vandelay

Reputation: 111

Instead of

while ((line = input.readLine()) != null) {
            output += (line + '\n');
        }

To output the results to the command line immediately just print within the while loop

     while ((line = input.readLine()) != null) {
         System.out.println(line);               
         output += (line + '\n');
      }

Upvotes: 2

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