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PowerBuilder

SSH Commands to a Cisco Switch

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Demonstrates establishing an SSH session with a Cisco switch (or similar device) and sending commands in a device console session. Each command is sent, and its output is read up to the device's next prompt.

Note: QuickShell allocates a PTY, which is what a network device console expects. The device presents an interactive prompt, and each command's output is read up to the next prompt.

Background: Network devices differ from general-purpose servers in that they expose a menu- or prompt-driven console rather than a Unix shell, so exec requests are usually unavailable and driving the interactive console is the only option. That makes prompt matching the synchronization mechanism, and it is why a PTY is appropriate here despite the general advice to avoid one. Retrieving the received text between commands is essential: a prompt left in the buffer would make the next receive return immediately with the wrong output.

Chilkat PowerBuilder Downloads

PowerBuilder
integer li_rc
integer li_Success
oleobject loo_Ssh
integer li_Port
string ls_Password
integer li_ChannelNum
integer li_CaseSensitive
string ls_CmdOutput

li_Success = 0

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  Demonstrates establishing an SSH session with a Cisco switch (or similar device) and sending
//  commands in a device console session.
//  
//  Note: QuickShell allocates a PTY, which is what a network device console expects.  The device
//  presents an interactive prompt, and each command's output is read up to the next prompt.

loo_Ssh = create oleobject
li_rc = loo_Ssh.ConnectToNewObject("Chilkat.Ssh")
if li_rc < 0 then
    destroy loo_Ssh
    MessageBox("Error","Connecting to COM object failed")
    return
end if

li_Port = 22
li_Success = loo_Ssh.Connect("172.16.16.100",li_Port)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    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.
ls_Password = "mySshPassword"

li_Success = loo_Ssh.AuthenticatePw("mySshLogin",ls_Password)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

//  Start a shell session.
li_ChannelNum = loo_Ssh.QuickShell()
if li_ChannelNum < 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

//  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
//  which means no limit -- without it, this call waits forever if the received data never
//  contains a match.
loo_Ssh.ReadTimeoutMs = 15000

li_CaseSensitive = 1

//  The switch presents a prompt ending in "#".  Reading up to it confirms the session is ready.
li_Success = loo_Ssh.ChannelReceiveUntilMatch(li_ChannelNum,"#","utf-8",li_CaseSensitive)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

ls_CmdOutput = loo_Ssh.GetReceivedText(li_ChannelNum,"utf-8")
if loo_Ssh.LastMethodSuccess = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

Write-Debug ls_CmdOutput

//  Send a command and read its output up to the next prompt.
li_Success = loo_Ssh.ChannelSendString(li_ChannelNum,"show clock~n","utf-8")
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

li_Success = loo_Ssh.ChannelReceiveUntilMatch(li_ChannelNum,"#","utf-8",li_CaseSensitive)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

//  Retrieving the text also clears the receive buffer, which matters: if the prompt were left
//  buffered, the next receive would match it immediately and return the wrong output.
ls_CmdOutput = loo_Ssh.GetReceivedText(li_ChannelNum,"utf-8")
if loo_Ssh.LastMethodSuccess = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

Write-Debug ls_CmdOutput

//  Additional commands follow the same send / read-to-prompt / retrieve pattern.
li_Success = loo_Ssh.ChannelSendString(li_ChannelNum,"show version~n","utf-8")
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

li_Success = loo_Ssh.ChannelReceiveUntilMatch(li_ChannelNum,"#","utf-8",li_CaseSensitive)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

ls_CmdOutput = loo_Ssh.GetReceivedText(li_ChannelNum,"utf-8")
if loo_Ssh.LastMethodSuccess = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

Write-Debug ls_CmdOutput

loo_Ssh.Disconnect()


destroy loo_Ssh