SSH Commands to a Cisco Switch

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Demonstrates establishing an SSH session with a Cisco switch (or similar device) and sending commands in a device console session. Each command is sent, and its output is read up to the device's next prompt.

Note: QuickShell allocates a PTY, which is what a network device console expects. The device presents an interactive prompt, and each command's output is read up to the next prompt.

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Ssh;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  ssh: TSsh;
  port: Integer;
  password: string;
  channelNum: Integer;
  caseSensitive: Boolean;
  cmdOutput: string;

begin
  success := False;

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

  //  Demonstrates establishing an SSH session with a Cisco switch (or similar device) and sending
  //  commands in a device console session.
  //  
  //  Note: QuickShell allocates a PTY, which is what a network device console expects.  The device
  //  presents an interactive prompt, and each command's output is read up to the next prompt.

  ssh := TSsh.Create;

  port := 22;
  success := ssh.Connect('172.16.16.100',port);
  if (success = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;

  //  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.
  password := 'mySshPassword';

  success := ssh.AuthenticatePw('mySshLogin',password);
  if (success = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;

  //  Start a shell session.
  channelNum := ssh.QuickShell();
  if (channelNum < 0) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;

  //  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;

  caseSensitive := True;

  //  The switch presents a prompt ending in "#".  Reading up to it confirms the session is ready.
  success := ssh.ChannelReceiveUntilMatch(channelNum,'#','utf-8',caseSensitive);
  if (success = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;

  cmdOutput := ssh.GetReceivedText(channelNum,'utf-8');
  if (ssh.LastMethodSuccess = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;
  WriteLn(cmdOutput);

  //  Send a command and read its output up to the next prompt.
  success := ssh.ChannelSendString(channelNum,'show clock' + #10,'utf-8');
  if (success = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;

  success := ssh.ChannelReceiveUntilMatch(channelNum,'#','utf-8',caseSensitive);
  if (success = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;

  //  Retrieving the text also clears the receive buffer, which matters: if the prompt were left
  //  buffered, the next receive would match it immediately and return the wrong output.
  cmdOutput := ssh.GetReceivedText(channelNum,'utf-8');
  if (ssh.LastMethodSuccess = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;
  WriteLn(cmdOutput);

  //  Additional commands follow the same send / read-to-prompt / retrieve pattern.
  success := ssh.ChannelSendString(channelNum,'show version' + #10,'utf-8');
  if (success = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;

  success := ssh.ChannelReceiveUntilMatch(channelNum,'#','utf-8',caseSensitive);
  if (success = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;

  cmdOutput := ssh.GetReceivedText(channelNum,'utf-8');
  if (ssh.LastMethodSuccess = False) then
    begin
      WriteLn(ssh.LastErrorText);
      Exit;
    end;
  WriteLn(cmdOutput);

  ssh.Disconnect();


  ssh.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.