Xojo Plugin

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
success = 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 New Chilkat.Ssh

Dim sshPort As Int32
sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
If (success = False) Then
    System.DebugLog(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
password = "mySshPassword"

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

//  Start two commands that will finish at different times.
Dim channel1 As Int32
channel1 = ssh.QuickCmdSend("sleep 2; echo first done")
If (channel1 < 0) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

Dim channel2 As Int32
channel2 = ssh.QuickCmdSend("echo second done")
If (channel2 < 0) Then
    System.DebugLog(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 Int32
pollTimeoutMs = 5000
Dim completedChannel As Int32
completedChannel = ssh.QuickCmdCheck(pollTimeoutMs)
While completedChannel <> -2
    If (completedChannel >= 0) Then
        Dim output As String
        output = ssh.GetReceivedText(completedChannel,"utf-8")
        If (ssh.LastMethodSuccess = False) Then
            System.DebugLog(ssh.LastErrorText)
            Return
        End If

        System.DebugLog("Channel " + Str(completedChannel) + " finished: " + output)
    End If

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

    completedChannel = ssh.QuickCmdCheck(pollTimeoutMs)
Wend

System.DebugLog("All quick commands have been collected.")

ssh.Disconnect