How Can I Execute System Commands in Java?

Executing System Commands in Java

This article discusses executing system commands in Java using the Runtime.exec() method. The method allows you to launch a separate process and interact with its standard input, output, and error streams.

To demonstrate its usage, consider the following code:

<code class="java">public class ImprovedCommandExecution {

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

            StringBuilder output = new StringBuilder();
            String line;
            while ((line = b.readLine()) != null) {
                output.append(line).append("\n");
            }

            b.close();

            System.out.println(output);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}</code>

In this example, we:

1. Get a reference to the Runtime object, which allows us to execute system commands.
2. Use exec() to start a process that executes the "uname -a" command.
3. Wait for the process to finish using waitFor().
4. Obtain the process's input stream and use a BufferedReader to read its output.
5. Append each line of output to a StringBuilder and print the final output.

This code stores the output from the system command in a String, making it easy to use within your Java program.

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