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SSH to a Cisco Switch - Processing "More" Responses

Demonstrates connecting to a Cisco switch, entering privileged mode with the ena command, and running a command whose response is paged. Each page ends with --More-- and requires a SPACE character to request the next page.

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: Paged output is the console equivalent of a pager like more, and a client must reproduce the keypress a human would make. Matching a set of patterns is what makes this tractable: each read ends either at the device prompt (output complete) or at --More-- (another page waiting), and the code branches accordingly. Note the prompt pattern includes the device name rather than a bare #, because that character also appears inside configuration text and would otherwise match far too early.

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llSuccess = .F.

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

//  Demonstrates connecting to a Cisco switch, entering privileged mode, and running a command
//  whose response is paged -- each page ends with "--More--" and requires a SPACE character to
//  request the next page.

loSsh = createobject("CkSsh")

lnPort = 22
llSuccess = loSsh.Connect("172.16.16.100",lnPort)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
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"

llSuccess = loSsh.AuthenticatePw("mySshLogin",lcPassword)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lnChannelNum = loSsh.QuickShell()
if (lnChannelNum < 0) then
    ? loSsh.LastErrorText
    release loSsh
    return
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

llCaseSensitive = .T.

//  In unprivileged mode the switch prompt ends with ">".
llSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,">","utf-8",llCaseSensitive)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lcReceived = loSsh.GetReceivedText(lnChannelNum,"utf-8")
if (loSsh.LastMethodSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

? lcReceived

//  Send "ena" to enter privileged mode.  Cisco devices expect a bare CR to terminate a command.
llSuccess = loSsh.ChannelSendString(lnChannelNum,"ena" + Chr(13),"utf-8")
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

llSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"Password:","utf-8",llCaseSensitive)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lcReceived = loSsh.GetReceivedText(lnChannelNum,"utf-8")
if (loSsh.LastMethodSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

? lcReceived

//  The enable password is separate from the login password, and likewise should come from a
//  secure source rather than being hard-coded.
lcEnablePassword = "myEnablePassword"
llSuccess = loSsh.ChannelSendString(lnChannelNum,lcEnablePassword,"utf-8")
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

llSuccess = loSsh.ChannelSendString(lnChannelNum,Chr(13),"utf-8")
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

//  In privileged mode the prompt ends with "#" instead of ">".
llSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"#","utf-8",llCaseSensitive)
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

lcReceived = loSsh.GetReceivedText(lnChannelNum,"utf-8")
if (loSsh.LastMethodSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

? lcReceived

//  Run a command whose output is delivered a page at a time.
llSuccess = loSsh.ChannelSendString(lnChannelNum,"show running-config" + Chr(13),"utf-8")
if (llSuccess = .F.) then
    ? loSsh.LastErrorText
    release loSsh
    return
endif

//  Each read ends either at the device prompt (output complete) or at "--More--" (another page
//  is waiting).  Match the full prompt rather than a bare "#", because "#" also appears inside
//  configuration text and would match too early.
loSaMatch = createobject("CkStringArray")
loSaMatch.Append("MySwitchName#")
loSaMatch.Append("--More--")

loSbReceived = createobject("CkStringBuilder")
llMoreComing = .T.

do while llMoreComing
    llSuccess = loSsh.ChannelReceiveUntilMatchN(lnChannelNum,loSaMatch,"utf-8",llCaseSensitive)
    if (llSuccess = .F.) then
        ? loSsh.LastErrorText
        release loSsh
        release loSaMatch
        release loSbReceived
        return
    endif

    loSbReceived.Clear()
    lcPageText = loSsh.GetReceivedText(lnChannelNum,"utf-8")
    if (loSsh.LastMethodSuccess = .F.) then
        ? loSsh.LastErrorText
        release loSsh
        release loSaMatch
        release loSbReceived
        return
    endif

    loSbReceived.Append(lcPageText)
    ? lcPageText

    //  If this page ended with "--More--", send a SPACE to request the next page.
    llMoreComing = loSbReceived.Contains("--More--",llCaseSensitive)
    if (llMoreComing) then
        llSuccess = loSsh.ChannelSendString(lnChannelNum," ","utf-8")
        if (llSuccess = .F.) then
            ? loSsh.LastErrorText
            release loSsh
            release loSaMatch
            release loSbReceived
            return
        endif

    endif

enddo

loSsh.Disconnect()


release loSsh
release loSaMatch
release loSbReceived