Connect to unix server through java

Question

Hi All,
I've seen this topic being discussed here, but I want to clarify my situation.
I'm a college student, so our school provides us accounts to a unix server.
I am writing a java program that needs to connect to this unix server owned by the school, and run some commands and obtain the results and display them in the same java program.
for example after the connection, I use the java Runtime() method to pass the "pwd" command from my program, and my java program should receive the result something like "/university/student/program" from the server, and I should be able to display in the java program.
I feel like since the unix from school is already acting as a "server," I don't need to write the server side code, it should be handled by the unix system, right?
Can someone give me a sample code on how to establish such connection?
BTW, I usually use ssh to access the unix server.
Much appreciated, and it's kinda urgent.
Thank You.

Answer 1

There are ssh clients written in Java so I'm not really sure you really want the following code because it accesses ssh using Runtime.exec(). I have never used this with anything except Linux so I assume that your client ssh is in a directory that is on the PATH.
If your server ssh is set up to do public key authentication then you will not have to supply the user password. If you do require a password then on Linux FC5 you will be prompted though a dialog. I don't know how you provide the password in Windows.
import java.io.*;
public class Fred117_1
    static class AsyncPipe implements Runnable
        public AsyncPipe(InputStream istrm, OutputStream ostrm)
            istrm_ = istrm;
            ostrm_= ostrm;
        public void run()
            try
                final byte[] buffer = new byte[1024];
                for (int length = 0; (length = istrm_.read(buffer)) != -1;)
                    ostrm_.write(buffer, 0, length);
            catch (Exception e)
                e.printStackTrace();
        private final OutputStream ostrm_;
        private final InputStream istrm_;
    public static void main(String[] args) throws Exception
        final boolean isWindows = System.getProperty("os.name").startsWith("Windows");
        final String LINE_SEPARATOR = System.getProperty("line.separator");
        final Process process = Runtime.getRuntime().exec(isWindows ? "cmd.exe" : "sh");
        new Thread(new AsyncPipe(process.getErrorStream(), System.err)).start();
        new Thread(new AsyncPipe(process.getInputStream(), System.out)).start();
        final Writer writer = new OutputStreamWriter(process.getOutputStream(), "UTF-8");
        final String[] shCommands =
            "ssh alpha",
            "df -k",
            "ls",
        for (String shCommand : shCommands)
            System.out.println(shCommand);
            writer.write(shCommand);
            writer.write(LINE_SEPARATOR);
        writer.close();
        final int returnCode = process.waitFor();
        System.out.println("Return code = " + returnCode);
}