How Can I Run CMD Commands and Change Directories from within a Java Program?

Running CMD Commands from Java

As you've discovered, executing CMD commands from within a Java program can be a tricky task. While there are numerous code snippets available online, it can be difficult to comprehend them all.

Let's start by addressing your goal of opening the CMD prompt:

public void excCommand(String new_dir){
    Runtime rt = Runtime.getRuntime();
    try {
        rt.exec(new String[]{"cmd.exe","/c","start"});

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

This code successfully opens the CMD prompt. To change to a different directory before running commands, you need to modify the command passed to rt.exec().

For instance, to change to the directory "C:Program FilesFlowella" and then run the "dir" command, use the following code:

ProcessBuilder builder = new ProcessBuilder(
    "cmd.exe", "/c", "cd \"C:\Program Files\Flowella\" && dir");
builder.redirectErrorStream(true);
Process p = builder.start();

The cd command is used to change directories, and the && operator ensures that the dir command is only executed if the directory change is successful. The redirectErrorStream(true) method combines the standard output and error streams into a single stream for easier processing.

Finally, reading the standard output of the process allows you to display the directory contents on the console.

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