Dart

SSH Exec (Execute Command Line)

Demonstrates running a single command on an SSH server with an exec request and retrieving its output. The example connects, authenticates, opens a session channel, sends the command, reads until the server closes the channel, and then checks the exit status.

Background: exec is the workhorse of SSH automation: it runs one command and the server closes the channel when the command exits, which is a definitive end-of-output signal. No PTY is involved, so the shell runs non-interactively — no prompt, no echoed input, no ANSI escape codes — giving clean, parseable output. Remember that an accepted exec request only means the request was accepted; the command's own success is reported through the channel exit status. Command syntax depends on the remote shell, which is the user's default shell on Linux/UNIX and usually CMD.EXE on Windows SSH servers.

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Dart

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 a single command on an SSH server with an exec request and retrieving
  // its output.  An exec request runs one command and the server closes the channel when it
  // finishes -- no PTY and no shell prompt are involved, so the output is clean and parseable.

  final ssh = CkSsh();

  // The hostname may be a hostname or an IP address.
  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;
  }

  // Open a session channel.  Several session channels may be open at once on one connection.
  final channelNum = ssh.openSessionChannel();
  if (channelNum < 0) {
    print(ssh.lastErrorText);
    return;
  }

  // The command syntax depends on the remote system's shell.  On Linux/UNIX it is typically the
  // user's default shell; on Windows SSH servers it is usually CMD.EXE.
  //   Linux/UNIX:  "ls -l /tmp"        or  "cd /etc; ls -la"
  //   Windows:     "dir"               or  "\"cd \\temp&&dir\""
  try {
    ssh.sendReqExec(channelNum, 'ls -l /tmp');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
  // it, this call waits forever if the server never sends channel close.
  ssh.readTimeoutMs = 15000;

  // Read the output until the server sends channel close, which happens when the command exits.
  try {
    ssh.channelReceiveToClose(channelNum);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  print(cmdOutput);

  // An accepted exec request does not mean the command succeeded.  Check the exit status.
  if (ssh.channelReceivedExitStatus(channelNum)) {
    print('Exit status: ${ssh.getChannelExitStatus(channelNum)}');
  }

  ssh.disconnect();
}