Ganymed SSH-2 for Java & Session.startShell() example

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PushbackInputStream;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedList;

import ch.ethz.ssh2.Connection;
import ch.ethz.ssh2.Session;
import ch.ethz.ssh2.StreamGobbler;

public class Main {
  public static String PROMPT = "GO1GO2GO3";
  final private static char LF = '\n';
  final private static char CR = '\r';

  public static String join(final Collection<String> str, final String sep) {
    final StringBuilder sb = new StringBuilder();
    final Iterator<String> i = str.iterator();
    while (i.hasNext()) {
      sb.append(i.next());
      if (i.hasNext()) {
        sb.append(sep);
      }
    }
    return sb.toString();
  }

  public static void main(String[] args) throws IOException {
    Connection c = new Connection("XXX");
    try {
      c.connect();
      if (!c.authenticateWithPassword("YYY", "ZZZ")) {
        throw new IOException("Authentification failed");
      }
      Session s = c.openSession();
      s.requestDumbPTY();
      s.startShell();
      try (InputStream is = s.getStdout();
           OutputStream os = s.getStdin();
           InputStream es = s.getStderr()) {
        final PushbackInputStream pbis = new PushbackInputStream(new StreamGobbler(is));
        writeCmd(os, pbis, "PS1=" + PROMPT);
        readTillPrompt(pbis, null);
        final Collection<String> lines = new LinkedList<>();
        writeCmd(os, pbis, "ls -l --color=never");
        readTillPrompt(pbis, lines);
        System.out.println("Out: " + join(lines, Character.toString(LF)));
        lines.clear();
        writeCmd(os, pbis, "free -m");
        readTillPrompt(pbis, lines);
        System.out.println("Out: " + join(lines, Character.toString(LF)));
        lines.clear();
      }
    } finally {
      c.close();
    }
  }

  public static void writeCmd(final OutputStream os,
                              final PushbackInputStream is,
                              final String cmd) throws IOException {
    System.out.println("In: " + cmd);
    os.write(cmd.getBytes());
    os.write(LF);
    skipTillEndOfCommand(is);
  }

  public static void readTillPrompt(final InputStream is,
                                    final Collection<String> lines) throws IOException {
    final StringBuilder cl = new StringBuilder();
    boolean eol = true;
    int match = 0;
    while (true) {
      final char ch = (char) is.read();
      switch (ch) {
      case CR:
      case LF:
        if (!eol) {
          if (lines != null) {
            lines.add(cl.toString());
          }
          cl.setLength(0);
        }
        eol = true;
        break;
      default:
        if (eol) {
          eol = false;
        }
        cl.append(ch);
        break;
      }

      if (cl.length() > 0
          && match < PROMPT.length()
          && cl.charAt(match) == PROMPT.charAt(match)) {
        match++;
        if (match == PROMPT.length()) {
          return;
        }
      } else {
        match = 0;
      }
    }
  }

  public static void skipTillEndOfCommand(final PushbackInputStream is) throws IOException {
    boolean eol = false;
    while (true) {
      final char ch = (char) is.read();
      switch (ch) {
      case CR:
      case LF:
        eol = true;
        break;
      default:
        if (eol) {
          is.unread(ch);
          return;
        }
      }
    }
  }
}