ifconfig works in linux terminal but it does not work in my app

Question

I have an android phone. It's rooted. I am trying to run ifconfig command. it works in Linux Terminal, but not works in Android Java Coding.

Environment

Android Version: android 10

Status: rooted

It works in Linux Terminal

I downloaded a Linux terminal in the Google App Store. I opened it, and running:

$ ifconfig

it lists a list of information that I need. it works perfectly.

It does not work in Android Java Coding

But when I type the same command in the Android app. it does not work. It shows nothing. bellow is the code that I ran:

            // Executes the command.
            Process process = Runtime.getRuntime().exec("/system/bin/ifconfig");

            // Reads stdout.
            // NOTE: You can write to stdin of the command using
            //       process.getOutputStream().
            BufferedReader reader = new BufferedReader(
                    new InputStreamReader(process.getInputStream()));
            int read;
            char[] buffer = new char[4096];
            StringBuffer output = new StringBuffer();
            while ((read = reader.read(buffer)) > 0) {
                output.append(buffer, 0, read);
            }
            reader.close();

            // Waits for the command to finish.
            process.waitFor();

            return output.toString();

I copied those codes from Run native executable code in android

Questions

Why it does not work in java code? Is there anything else I missed?

Answer 1

Thanks @Erlkoenig mentions. I ran it with su grant permission.

bellow is my changed code:

            // Executes the command.
            Process process = Runtime.getRuntime().exec("su");

            // Writes stdin
            BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(process.getOutputStream()));
            String command = "/system/bin/ifconfig";
            writer.write(command.toCharArray());
            writer.flush();
            writer.close();

            // Reads stdout.
            BufferedReader reader = new BufferedReader(
                    new InputStreamReader(process.getInputStream()));
            int read;
            char[] buffer = new char[4096];
            StringBuffer output = new StringBuffer();
            while ((read = reader.read(buffer)) > 0) {
                output.append(buffer, 0, read);
            }
            reader.close();

            // Waits for the command to finish.
            process.waitFor();

            return output.toString();

remember to close writer, after had written the command into stdin.