B4X

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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Dim success As Boolean = False

'  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.

Dim ssh As ChilkatSsh
ssh.Initialize("ssh")

Dim sshPort As Int = 22
success = ssh.Connect("ssh.example.com", sshPort)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  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.
Dim password As String = "mySshPassword"

success = ssh.AuthenticatePw("mySshLogin", password)
If success = False Then
    Log(ssh.LastErrorText)
    Return
End If


'  Start two commands that will finish at different times.
Dim channel1 As Int = ssh.QuickCmdSend("sleep 2; echo first done")
If channel1 < 0 Then
    Log(ssh.LastErrorText)
    Return
End If


Dim channel2 As Int = ssh.QuickCmdSend("echo second done")
If channel2 < 0 Then
    Log(ssh.LastErrorText)
    Return
End If


'  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).
Dim pollTimeoutMs As Int = 5000
Dim completedChannel As Int = ssh.QuickCmdCheck(pollTimeoutMs)
Do While completedChannel <> -2
    If completedChannel >= 0 Then
        Dim output As String = ssh.GetReceivedText(completedChannel, "utf-8")
        If ssh.LastMethodSuccess = False Then
            Log(ssh.LastErrorText)
            Return
        End If

        Log("Channel " & completedChannel & " finished: " & output)
    End If


    If completedChannel = -1 Then
        Log("Still waiting for a command to finish...")
    End If


    completedChannel = ssh.QuickCmdCheck(pollTimeoutMs)
Loop

Log("All quick commands have been collected.")

ssh.Disconnect