Delphi ActiveX

Collect Completed SSH Commands with QuickCmdCheck

Demonstrates the Chilkat Ssh.QuickCmdCheck method, which waits for any command started by QuickCmdSend to complete. The only argument is the poll timeout in milliseconds; 0 performs a nonblocking check. It returns the channel number of a completed command, -1 when commands are still pending but none finished before the timeout, or -2 when no quick commands remain or an error occurred.

Background: This is the collection half of the concurrent pattern. Each completed channel is reported only once, so looping until -2 drains every outstanding command exactly once. Distinguish the two negative values carefully: -1 simply means "still working, ask again," while -2 means there is nothing left to wait for — or that the connection failed, so check LastErrorText when the distinction matters. Manually opened exec channels are not reported here.

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var
success: Integer;
ssh: TChilkatSsh;
sshPort: Integer;
password: WideString;
channel1: Integer;
channel2: Integer;
pollTimeoutMs: Integer;
completedChannel: Integer;
output: WideString;

begin
success := 0;

//  Demonstrates the Ssh.QuickCmdCheck method, which waits for any command started by
//  QuickCmdSend to complete.  The only argument is the poll timeout in milliseconds; 0 performs
//  a nonblocking check.

ssh := TChilkatSsh.Create(Self);

sshPort := 22;
success := ssh.Connect('ssh.example.com',sshPort);
if (success = 0) then
  begin
    Memo1.Lines.Add(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 = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

//  Start two commands that will finish at different times.
channel1 := ssh.QuickCmdSend('sleep 2; echo first done');
if (channel1 < 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

channel2 := ssh.QuickCmdSend('echo second done');
if (channel2 < 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

//  Collect the results as they complete.  The return value is the channel number of a completed
//  command, -1 if commands are still pending but none finished before the timeout, or -2 when
//  no quick commands remain (or an error occurred).
pollTimeoutMs := 5000;
completedChannel := ssh.QuickCmdCheck(pollTimeoutMs);
while completedChannel <> -2 do
  begin
    if (completedChannel >= 0) then
      begin
        output := ssh.GetReceivedText(completedChannel,'utf-8');
        if (ssh.LastMethodSuccess = 0) then
          begin
            Memo1.Lines.Add(ssh.LastErrorText);
            Exit;
          end;
        Memo1.Lines.Add('Channel ' + IntToStr(completedChannel) + ' finished: ' + output);
      end;

    if (completedChannel = -1) then
      begin
        Memo1.Lines.Add('Still waiting for a command to finish...');
      end;

    completedChannel := ssh.QuickCmdCheck(pollTimeoutMs);
  end;

Memo1.Lines.Add('All quick commands have been collected.');

ssh.Disconnect();