How to execute system commands (linux/bsd) using Java

Question

I am attempting to be cheap and execute a local system command (uname -a) in Java. I am looking to grab the output from uname and store it in a String. What is the best way of doing this? Current code:

public class lame {

    public static void main(String args[]) {
        try {
            Process p = Runtime.getRuntime().exec("uname -a");
            p.waitFor();
            BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
            String line=reader.readLine();

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

        }
        catch(IOException e1) {}
        catch(InterruptedException e2) {}

        System.out.println("finished.");
    }
}

Answer 1

Your way isn't far off from what I'd probably do:

Runtime r = Runtime.getRuntime(); Process p = r.exec("uname -a"); p.waitFor(); BufferedReader b = new BufferedReader(new InputStreamReader(p.getInputStream())); String line = "";  while ((line = b.readLine()) != null) {   System.out.println(line); }  b.close(); 

Handle whichever exceptions you care to, of course.

Answer 2

That is the best way to do it. Also you can use the ProcessBuilder which has a variable argument constructor, so you could save a line or two of code

Answer 3

What you are doing looks fine. If your command is only returning a single string, you don't need the while loop, just store the reader.readLine() value in a single String variable.

Also, you probably should do something with those exceptions, rather than just swallowing them.

Answer 4

I know this is very old but still...

Reading the article here: http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html
It is my understanding that you should first read the output and error streams of your executed command and only then waitFor the return value of your process.