SSH Remote Shell with Multiple Commands

See more SSH Examples

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.

import 'package:chilkat/chilkat.dart';

void main() {
  // 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.

  final ssh = CkSsh();

  final hostname = 'ssh.example.com';
  final port = 22;
  try {
    ssh.connect(hostname, port);
  } on ChilkatException catch (e) {
    print(e.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.
  final password = 'mySshPassword';

  try {
    ssh.authenticatePw('mySshLogin', password);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final channelNum = ssh.openSessionChannel();
  if (channelNum < 0) {
    print(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.
  try {
    ssh.sendReqShell(channelNum);
  } on ChilkatException catch (e) {
    print(e.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.readTimeoutMs = 15000;

  final caseSensitive = true;

  // ---- 1st command: change directory ----
  try {
    ssh.channelSendString(channelNum, 'cd /tmp; echo END_OF_CMD_1\n', 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    ssh.channelReceiveUntilMatch(channelNum, 'END_OF_CMD_1', 'utf-8', caseSensitive);
  } on ChilkatException catch (e) {
    print(e.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;
  try {
    cmdOutput = ssh.getReceivedText(channelNum, 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print(cmdOutput);

  // ---- 2nd command: directory listing ----
  try {
    ssh.channelSendString(channelNum, 'ls; echo END_OF_CMD_2\n', 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    ssh.channelReceiveUntilMatch(channelNum, 'END_OF_CMD_2', 'utf-8', caseSensitive);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    cmdOutput = ssh.getReceivedText(channelNum, 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print(cmdOutput);

  // ---- 3rd command: long listing, then finish the session ----
  try {
    ssh.channelSendString(channelNum, 'ls -l\n', 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // No more input will be sent.
  try {
    ssh.channelSendEof(channelNum);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    ssh.channelReceiveToClose(channelNum);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    cmdOutput = ssh.getReceivedText(channelNum, 'utf-8');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print(cmdOutput);

  ssh.disconnect();
}