VB.NET

Get Text Received on the SSH stderr Buffer

Demonstrates the Chilkat Ssh.GetReceivedStderrText method, which decodes and returns the text accumulated in a channel's separate stderr buffer. The first argument is the channel number and the second is the charset. The stderr buffer is cleared after the text is returned.

Background: This is only meaningful when StderrToStdout is false, which keeps error output in its own buffer instead of merging it into the normal receive buffer. Separating the two lets a program parse a command's real output cleanly while still capturing diagnostics — important because many Unix tools write warnings to stderr that would otherwise corrupt the parsed result. With merging enabled, this buffer stays empty and the text appears via GetReceivedText instead.

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Dim success As Boolean = False

'  Demonstrates the Ssh.GetReceivedStderrText method, which decodes and returns the text in a
'  channel's separate stderr buffer.  The 1st argument is the channel number and the 2nd is the
'  charset.  The stderr buffer is cleared after the text is returned.

Dim ssh As New Chilkat.Ssh

Dim sshPort As Integer = 22
success = ssh.Connect("ssh.example.com",sshPort)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
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
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


'  Keep stderr in its own buffer rather than merging it into the normal receive buffer.
ssh.StderrToStdout = False

Dim channelNum As Integer = ssh.OpenSessionChannel()
If (channelNum < 0) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


'  Run a command that writes to both stdout and stderr.
success = ssh.SendReqExec(channelNum,"ls /etc/hosts /no/such/path")
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


'  IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
'  it, this call waits forever if the server never sends channel close.
ssh.ReadTimeoutMs = 15000

success = ssh.ChannelReceiveToClose(channelNum)
If (success = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


Dim stdoutText As String = ssh.GetReceivedText(channelNum,"utf-8")
If (ssh.LastMethodSuccess = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("STDOUT: " & stdoutText)

Dim stderrText As String = ssh.GetReceivedStderrText(channelNum,"utf-8")
If (ssh.LastMethodSuccess = False) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("STDERR: " & stderrText)

ssh.Disconnect()