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I'm trying to get result from a command through VB.NET, it is returning empty string as shown in the below code:

Dim connInfo As New Renci.SshNet.PasswordConnectionInfo(serverip, user, pass)
Dim sshClient As New Renci.SshNet.SshClient(connInfo)

Dim cmd As Renci.SshNet.SshCommand
Using sshClient
    sshClient.Connect()

    cmd = sshClient.RunCommand("opmnctl status -l")
    MsgBox(cmd.Result)

    sshClient.Disconnect()
End Using

While when I try with normal command like "ls -ltr" it returns the result successfully.

Is there another way of fetching result string? Or are opmnctl commands for OPMN Oracle engine not supported on Renci? Any help would be appreciated.

Martin Prikryl
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Hesham Saeed
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1 Answers1

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If the opmnctl fails for some reason, it might have produced a message on the error output.

So check also cmd.Error and cmd.ExitStatus.

Note that the .RunCommand method uses a non-interactive terminal, what may cause problems with some commands.

Particularly a different environment may be set, when the non-interactive terminal is used as a different set of startup scripts is executed and/or different branches in the scripts are taken (based on a value of a TERM environment variable).

In your case, it seems that the opmnctl is not included in PATH on non-interactive terminals.

You should get the same issue when you force the non-interactive terminal in your SSH client.

For example:

  • With OpenSSH command-line ssh client, use -T switch (Disable pseudo-tty allocation).

    ssh -T user@host opmnctl status -l

  • The same with PLink (from PuTTY package)

    plink.exe -T user@host opmnctl status -l

(The -T should be implicit when command is specified on command-line anyway)

Solution are:

  • Fix your startup scripts to include the opmnctl to PATH even on non-interactive terminals (preferred)
  • Use a full path to opmnctl in your command.
  • Modify SSH.NET code to issue SendPseudoTerminalRequest request in .RunCommand implementation (I didn't test this).
Martin Prikryl
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