Example reading and writing using exec channel

JschExec.java

class JschExec {
  private static String runCommand(Session session, String command, String... input) throws JSchException, IOException {

        ChannelExec channel = (ChannelExec) session.openChannel("exec");
        try {
            channel.setCommand(command);
            logger.debug("running command: {}", command);

            final InputStream in = channel.getInputStream();
            final InputStream errStream = channel.getErrStream();
            final OutputStream out = channel.getOutputStream();
            PrintWriter writer = new PrintWriter(out, true);
            channel.connect();

            int printed=0;
            while (true) {

                String response = null;
                String errorMessage = null;

                while (in.available() > 0) {
                    byte[] tmp = new byte[1024];
                    int i = in.read(tmp, 0, 1024);
                    if (i < 0) break;
                    response = new String(tmp, 0, i, Charset.defaultCharset());
                }

                while (errStream.available() > 0) {
                    byte[] tmp = new byte[1024];
                    int i = errStream.read(tmp, 0, 1024);
                    if (i < 0) break;
                    errorMessage = new String(tmp, Charset.defaultCharset());
                }

                logger.debug("exit-status: {}", channel.getExitStatus());
                logger.debug("stderr:{}", errorMessage);
                logger.debug("stdout: {}", response);

                if (channel.isClosed()) {
                    if (channel.getExitStatus() == 0) {
                        return response;
                    } else {
                        throw new RuntimeException("command ended in exit-status:" + channel.getExitStatus() +
                                " with error message: " + errorMessage);
                    }

                } else if (response != null) {
                    writer.println(input[printed++]);
                }

                Thread.sleep(50);
            }
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw new RuntimeException(e);
        } finally {
            channel.disconnect();
        }
    }
}