SSH to a Cisco Switch - Processing "More" Responses

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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.

local chilkat = require("chilkat")

-- 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.

local ssh = chilkat.Ssh.new()

local port = 22
local success = ssh:connect("172.16.16.100", port)
if not success then
    print(ssh.last_error_text)
    return
end

-- 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.
local password = "mySshPassword"

success = ssh:authenticate_pw("mySshLogin", password)
if not success then
    print(ssh.last_error_text)
    return
end

local channelNum = ssh:quick_shell()
if channelNum < 0 then
    print(ssh.last_error_text)
    return
end

-- 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.
ssh.read_timeout_ms = 15000

local caseSensitive = true

-- In unprivileged mode the switch prompt ends with ">".
success = ssh:channel_receive_until_match(channelNum, ">", "utf-8", caseSensitive)
if not success then
    print(ssh.last_error_text)
    return
end

local received = ssh:get_received_text(channelNum, "utf-8")
if not ssh.last_method_success then
    print(ssh.last_error_text)
    return
end

print(received)

-- Send "ena" to enter privileged mode.  Cisco devices expect a bare CR to terminate a command.
success = ssh:channel_send_string(channelNum, "ena\r", "utf-8")
if not success then
    print(ssh.last_error_text)
    return
end

success = ssh:channel_receive_until_match(channelNum, "Password:", "utf-8", caseSensitive)
if not success then
    print(ssh.last_error_text)
    return
end

received = ssh:get_received_text(channelNum, "utf-8")
if not ssh.last_method_success then
    print(ssh.last_error_text)
    return
end

print(received)

-- The enable password is separate from the login password, and likewise should come from a
-- secure source rather than being hard-coded.
local enablePassword = "myEnablePassword"
success = ssh:channel_send_string(channelNum, enablePassword, "utf-8")
if not success then
    print(ssh.last_error_text)
    return
end

success = ssh:channel_send_string(channelNum, "\r", "utf-8")
if not success then
    print(ssh.last_error_text)
    return
end

-- In privileged mode the prompt ends with "#" instead of ">".
success = ssh:channel_receive_until_match(channelNum, "#", "utf-8", caseSensitive)
if not success then
    print(ssh.last_error_text)
    return
end

received = ssh:get_received_text(channelNum, "utf-8")
if not ssh.last_method_success then
    print(ssh.last_error_text)
    return
end

print(received)

-- Run a command whose output is delivered a page at a time.
success = ssh:channel_send_string(channelNum, "show running-config\r", "utf-8")
if not success then
    print(ssh.last_error_text)
    return
end

-- 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.
local saMatch = chilkat.StringArray.new()
saMatch:append("MySwitchName#")
saMatch:append("--More--")

local sbReceived = chilkat.StringBuilder.new()
local moreComing = true

while moreComing do
    success = ssh:channel_receive_until_match_n(channelNum, saMatch, "utf-8", caseSensitive)
    if not success then
        print(ssh.last_error_text)
        return
    end

    sbReceived:clear()
    local pageText = ssh:get_received_text(channelNum, "utf-8")
    if not ssh.last_method_success then
        print(ssh.last_error_text)
        return
    end

    sbReceived:append(pageText)
    print(pageText)

    -- If this page ended with "--More--", send a SPACE to request the next page.
    moreComing = sbReceived:contains("--More--", caseSensitive)
    if moreComing then
        success = ssh:channel_send_string(channelNum, " ", "utf-8")
        if not success then
            print(ssh.last_error_text)
            return
        end
    end
end

ssh:disconnect()