Java

SSH Remote Shell with Multiple Commands

Demonstrates running several commands one after another in a single remote shell session, retrieving each command's output separately. No PTY is requested, so each command is followed by an echoed marker that signals where its output ends.

Background: Interleaving commands and reads in one shell requires a way to know where each command's output stops. An interactive session would use the shell prompt, but without a PTY the shell is non-interactive and never prints one — so the dependable technique is to append echo SOME_MARKER to each command and read up to that marker. Retrieving the text also clears the receive buffer, which matters here: if a marker were left buffered, the next receive would match it immediately and return the wrong output.

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Java

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;

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    //  Demonstrates running several commands one after another in a single remote shell session,
    //  retrieving each command's output separately.
    //  
    //  No PTY is requested, so the shell runs non-interactively and never prints a command prompt.
    //  Because there is no prompt to synchronize on, each command is followed by an "echo" of a
    //  unique marker, and the output is read up to that marker.

    CkSsh ssh = new CkSsh();

    String hostname = "ssh.example.com";
    int port = 22;
    success = ssh.Connect(hostname,port);
    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;
        }

    //  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
    //  which means no limit -- without it, this call waits forever if the received data never
    //  contains a match.
    ssh.put_ReadTimeoutMs(15000);

    boolean caseSensitive = true;

    //  ---- 1st command: change directory ----
    success = ssh.ChannelSendString(channelNum,"cd /tmp; echo END_OF_CMD_1\n","utf-8");
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    success = ssh.ChannelReceiveUntilMatch(channelNum,"END_OF_CMD_1","utf-8",caseSensitive);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    //  Retrieving the text also clears the receive buffer, which matters: if the next marker were
    //  left in the buffer, the following receive would match immediately.
    String cmdOutput = ssh.getReceivedText(channelNum,"utf-8");
    if (ssh.get_LastMethodSuccess() == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    System.out.println(cmdOutput);

    //  ---- 2nd command: directory listing ----
    success = ssh.ChannelSendString(channelNum,"ls; echo END_OF_CMD_2\n","utf-8");
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    success = ssh.ChannelReceiveUntilMatch(channelNum,"END_OF_CMD_2","utf-8",caseSensitive);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

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

    System.out.println(cmdOutput);

    //  ---- 3rd command: long listing, then finish the session ----
    success = ssh.ChannelSendString(channelNum,"ls -l\n","utf-8");
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    //  No more input will be sent.
    success = ssh.ChannelSendEof(channelNum);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    success = ssh.ChannelReceiveToClose(channelNum);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

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

    System.out.println(cmdOutput);

    ssh.Disconnect();
  }
}