Assistance needed: Capturing $stream.Read() response without issuing "blind" Start-Sleep command afterwards

Considering there are a couple of known issues with Cisco devices and Posh-SSH, I have to use SSH streams in Posh-SSH.

Hence, I created a PS function Send-SSHCommand(below) which will send any sequence of commands to a Cisco device; and, return the output as FAST as possible.

Instead of putting a blind Start-Sleep 5 command after issuing $ResponseRaw = $stream.Read(), I would like to use a clever way to wait the minimum amount of time (before reading the entire stream) by using some kind of while command. For example: while (!($stream.EndExpect("$DeviceName#"))) { Start-Sleep 60 }. I know that I can’t use the method .EndExpect like that. But, I think you’ll at least understand my goal.

Note: The only thing I know for sure is that the end of the output ALWAYS ends with $DeviceName#.

function Send-SSHCommand {
    Param(
        [Parameter(Mandatory=$true)]
        [Array]$Commands,
        [Parameter(Mandatory=$false)]
        [string]$DeviceName
    )

    BEGIN       {
                    $Final = @()
                    remove-variable Response -ErrorAction SilentlyContinue
                    Get-SSHSession | select SessionId | Remove-SSHSession | Out-Null
                    New-SSHSession -ComputerName $DeviceName -AcceptKey -Credential $Credential -ErrorAction SilentlyContinue | Out-Null
                    while ((Get-SSHSession).Host -ne $DeviceName) {      
                    
                        New-SSHSession -ComputerName $DeviceName -AcceptKey -Credential $Credential -ErrorAction SilentlyContinue | Out-Null
                        sleep -mill 500
                    }

                    $session = Get-SSHSession -Index 0 
                    $stream = $session.Session.CreateShellStream("dumb", 0, 0, 0, 0, 1000)
                    $stream.Write("terminal Length 0`n")
                    sleep -mill 60
                    $stream.Read() | Out-Null
                }

    PROCESS {

                foreach ($Command in $Commands)
                {
                    $stream.Write("$Command`n")                    

                    Start-Sleep 5
                    # while (!($stream.EndExpect("$DeviceName#"))) { Start-Sleep 60 }
                    # while ($stream.DataAvailable -eq $true) { Start-Sleep 60 }
                    # $stream.WriteTimeout = 5000

                    $ResponseRaw = $stream.Read()                    
                    $Response = $ResponseRaw -split "`r`n" | %{$_.trim()}
                    $Response = $Response | ?{$_ -NotMatch "$DeviceName#"}
                    $Final += $Response
                }
            }

    END     {
                Return $Final
                $stream.Write("exit`n")
                Remove-SSHSession -Index 0 | Out-Null
            }

}

Command: Send-SSHCommand -DeviceName “Cisco-device01” -Commands "sho log | include Aug 2.*

[mkanet]

@MVKozlov EDIT: Update. I was able to finally use the “correct” way to use New-SSHSession every time. It works every time. I am now using the below code:

do {
    $session = New-SSHSession -ComputerName $DeviceName -AcceptKey -Credential $Credential -force
} until ($session -ne $null -and $session.Connected)

All issues are now resolved. Thanks again for your time!

[darkoperator]

Actually expect was what I was going to recomment because it is what I use for sudo. Never dealt with an expired password. That is why I made this function https://github.com/darkoperator/Posh-SSH/blob/master/docs/Invoke-SSHStreamExpectSecureAction.md

Sent from my iPhone

On Aug 25, 2022, at 8:41 AM, MKANET @.***> wrote:

Looked at Expect() in Renci source

This is definitely not what you need EndExpect() it’s a async companion to BeginExpect()

And Expect() itself is equal to Read() and match(), i.e. it wait for some string or regex and drop all intermediate output

I think I’ll need to wait for darkoperator for this. I wasn’t able to figure out an effective way to take advantage of the available methods and properties for stream to wait the minimum amount of time between $stream.Write(“$Command``n”) and $stream.read()

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