Read Data from an SSH Channel

See more SSH Examples

Demonstrates the Chilkat Ssh.ChannelRead method, which reads incoming SSH channel messages. The only argument is the channel number; the ReadTimeoutMs property limits how long it waits. Received data is appended to the channel's receive buffer, then retrieved with a GetReceived... method.

The integer return value is -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or channel close was processed, or — when greater than 0 — the total bytes currently buffered for the channel (not the bytes newly received by this call).

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    //  Demonstrates the Ssh.ChannelRead method, which reads incoming SSH channel messages.  The only
    //  argument is the channel number.  The ReadTimeoutMs property limits how long it waits.

    CkSsh ssh = new CkSsh();

    int sshPort = 22;
    success = ssh.Connect("ssh.example.com",sshPort);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    //  Normally you would not hard-code the password in source.  You should instead obtain it
    //  from an interactive prompt, environment variable, or a secrets vault.
    String password = "mySshPassword";

    success = ssh.AuthenticatePw("mySshLogin",password);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    int channelNum = ssh.OpenSessionChannel();
    if (channelNum < 0) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    //  Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
    //  raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
    //  echo typed commands back, and skips interactive login scripts.  The output is therefore
    //  clean and easily parseable -- but because no prompt is ever sent, code must not wait for
    //  one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
    success = ssh.SendReqShell(channelNum);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    success = ssh.ChannelSendString(channelNum,"uname -a\n","utf-8");
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    //  The return value is: -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or
    //  channel close was processed, or the total number of buffered bytes when greater than 0.
    int result = ssh.ChannelRead(channelNum);
    if (result == -1) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    if (result == -2) {
        System.out.println("No channel data arrived before the timeout.");
        }

    if (result == 0) {
        System.out.println("EOF or channel close was processed.  Buffered data may still remain.");
        }

    if (result > 0) {
        System.out.println("Total bytes buffered: " + result);
        }

    String output = ssh.getReceivedText(channelNum,"utf-8");
    if (ssh.get_LastMethodSuccess() == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    System.out.println(output);

    ssh.Disconnect();
  }
}