How to execute a bash script from java program

Question

I would like my Java program to execute a bash script and return the output back to Java. The trick is my script starts some sort of 'interactive session' and I suppose that is why my Java application freezes (Enters an infinite loop I suppose). Here is the code I use to execute the script, I use ProcessBuilder in order to do that. I also tried

Runtime.getRuntime().exec(PathToScript);

It doesn't work either.

public class test1 {
public static void main(String a[]) throws InterruptedException, IOException {

    List<String> commands = new ArrayList<String>();
    List<String> commands1 = new ArrayList<String>();

    commands.add("/Path/To/Script/skrypt3.sh");
    commands.add("> /dev/ttys002");



    ProcessBuilder pb = new ProcessBuilder(commands);
    pb.redirectErrorStream(true);
    try {

        Process prs = pb.start();
        Thread inThread = new Thread(new In(prs.getInputStream()));
        inThread.start();
        Thread.sleep(1000);
        OutputStream writeTo = prs.getOutputStream();
       writeTo.write("oops\n".getBytes());
        writeTo.flush();
        writeTo.close();

    } catch (IOException e) {
        e.printStackTrace();

    }
}
}

class In implements Runnable {

private InputStream is;

public In(InputStream is) {
    this.is = is;
}

@Override
public void run() {
    try {
        byte[] b = new byte[1024];
        int size = 0;
        while ((size = is.read(b)) != -1) {



            System.out.println(new String(b));
        }
        is.close();
    } catch (IOException ex) {
        Logger.getLogger(In.class.getName()).log(Level.SEVERE, null, ex);
    }

}
}

And here is the script I try to execute. It works like a charm when I run it directly from terminal.

#!/bin/bash          
drozer console connect << EOF > /dev/ttys002
permissions
run app.package.info -a com.mwr.example.sieve
exit
EOF

Answer 1

You should not be trying to add redirect instructions as part of the command name:

commands.add("/Path/To/Script/skrypt3.sh");
commands.add("> /dev/ttys002");
ProcessBuilder pb = new ProcessBuilder(commands);

Instead, use the redirectOutput method, something like this:

tty = new File("/dev/ttys002");
ProcessBuilder pb = new ProcessBuilder("/Path/To/Script/skrypt3.sh")
    .redirectOutput(ProcessBuilder.Redirect.appendTo(tty))
    .redirectError(ProcessBuilder.Redirect.appendTo(tty))
    .start();

Though, it appears your bash script is already handling the redirection so not sure you need to do that in Java.

See this answer for more info.