Visual FoxPro

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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LOCAL lnSuccess
LOCAL loSsh
LOCAL lnPort
LOCAL lcPassword
LOCAL lnChannelNum
LOCAL lnCaseSensitive
LOCAL lcReceived
LOCAL lcEnablePassword
LOCAL loSaMatch
LOCAL loSbReceived
LOCAL lnMoreComing
LOCAL lcPageText

lnSuccess = 0

*  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('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

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

*  In unprivileged mode the switch prompt ends with ">".
lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,">","utf-8",lnCaseSensitive)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

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

? lcReceived

*  Send "ena" to enter privileged mode.  Cisco devices expect a bare CR to terminate a command.
lnSuccess = loSsh.ChannelSendString(lnChannelNum,"ena" + CHR(13),"utf-8")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

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

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

lnSuccess = loSsh.ChannelSendString(lnChannelNum,CHR(13),"utf-8")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

*  In privileged mode the prompt ends with "#" instead of ">".
lnSuccess = loSsh.ChannelReceiveUntilMatch(lnChannelNum,"#","utf-8",lnCaseSensitive)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

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

? lcReceived

*  Run a command whose output is delivered a page at a time.
lnSuccess = loSsh.ChannelSendString(lnChannelNum,"show running-config" + CHR(13),"utf-8")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
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('Chilkat.StringArray')
loSaMatch.Append("MySwitchName#")
loSaMatch.Append("--More--")

loSbReceived = CreateObject('Chilkat.StringBuilder')
lnMoreComing = 1

DO WHILE lnMoreComing
    lnSuccess = loSsh.ChannelReceiveUntilMatchN(lnChannelNum,loSaMatch,"utf-8",lnCaseSensitive)
    IF (lnSuccess = 0) THEN
        ? loSsh.LastErrorText
        RELEASE loSsh
        RELEASE loSaMatch
        RELEASE loSbReceived
        CANCEL
    ENDIF

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

    loSbReceived.Append(lcPageText)
    ? lcPageText

    *  If this page ended with "--More--", send a SPACE to request the next page.
    lnMoreComing = loSbReceived.Contains("--More--",lnCaseSensitive)
    IF (lnMoreComing) THEN
        lnSuccess = loSsh.ChannelSendString(lnChannelNum," ","utf-8")
        IF (lnSuccess = 0) THEN
            ? loSsh.LastErrorText
            RELEASE loSsh
            RELEASE loSaMatch
            RELEASE loSbReceived
            CANCEL
        ENDIF

    ENDIF

ENDDO

loSsh.Disconnect()

RELEASE loSsh
RELEASE loSaMatch
RELEASE loSbReceived