Visual FoxPro

SSH Commands to a Cisco Switch

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.

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LOCAL lnSuccess
LOCAL loSsh
LOCAL lnPort
LOCAL lcPassword
LOCAL lnChannelNum
LOCAL lnCaseSensitive
LOCAL lcCmdOutput

lnSuccess = 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.

loSsh = CreateObject('Chilkat.Ssh')

lnPort = 22
lnSuccess = loSsh.Connect("172.16.16.100",lnPort)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

*  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.
lcPassword = "mySshPassword"

lnSuccess = loSsh.AuthenticatePw("mySshLogin",lcPassword)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

*  Start a shell session.
lnChannelNum = loSsh.QuickShell()
IF (lnChannelNum < 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

*  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.
loSsh.ReadTimeoutMs = 15000

lnCaseSensitive = 1

*  The switch presents a prompt ending in "#".  Reading up to it confirms the session is ready.
lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"#","utf-8",lnCaseSensitive)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lcCmdOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
IF (loSsh.LastMethodSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

? lcCmdOutput

*  Send a command and read its output up to the next prompt.
lnSuccess = loSsh.ChannelSendString(lnChannelNum,"show clock" + CHR(10),"utf-8")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"#","utf-8",lnCaseSensitive)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

*  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.
lcCmdOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
IF (loSsh.LastMethodSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

? lcCmdOutput

*  Additional commands follow the same send / read-to-prompt / retrieve pattern.
lnSuccess = loSsh.ChannelSendString(lnChannelNum,"show version" + CHR(10),"utf-8")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"#","utf-8",lnCaseSensitive)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lcCmdOutput = loSsh.GetReceivedText(lnChannelNum,"utf-8")
IF (loSsh.LastMethodSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

? lcCmdOutput

loSsh.Disconnect()

RELEASE loSsh