Run sudo command using Java processBuilder

Question

I need to run a sudo command from within java, and redirect the output to a file, using processbuilder or similar.

Two questions:

1. Will piping the sudo password using echo work as follows?

2. Although the file gets created, nothing is ever written to it. Any ideas why?

   ProcessBuilder conntrack_process = new ProcessBuilder("/bin/bash", "-c", "echo '<passwordhere>' | sudo conntrack -L");
   conntrack_process.redirectOutput(new java.io.File("/home/<homedir>/conntrack_out.txt"));
   Process ct_process = conntrack_process.start();
   ct_process.waitFor();
   ct_process.destroy();
   

I am using Ubuntu 16.04.

Answer 1

First, you need to use -S with sudo to make it read the password from its stdin.
Second, you should read or redirect the error stream somewhere to be aware of any errors.