Lua

Receive from an SSH Channel Until a Pattern Matches

Demonstrates the Chilkat Ssh.ChannelReceiveUntilMatch method, which receives text until the accumulated text matches a pattern. The arguments are the channel number, the pattern, the charset, and whether matching is case-sensitive. Existing buffered text is checked before waiting for more network data.

Important: Set the ReadTimeoutMs property before calling this method. It defaults to 0, meaning no limit, so without it the call waits forever if the received data never contains a match.

Background: Driving a shell channel means knowing when the remote side has finished talking. With no PTY requested the shell is non-interactive and never prints a prompt, so the reliable signal is a marker you deliberately echo after your command. This method automates "read until you see X." The pattern syntax is deliberately minimal: literal characters plus *, which matches zero or more characters and can span line breaks. ? and bracket classes are not supported, and backslash does not escape a literal *.

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Lua

local chilkat = require("chilkat")

-- Demonstrates the Ssh.ChannelReceiveUntilMatch method, which receives text until the
-- accumulated text matches a pattern.  The 1st argument is the channel number, the 2nd is the
-- pattern, the 3rd is the charset, and the 4th selects case-sensitive matching.  The pattern
-- supports literal characters plus "*", which matches zero or more characters.

local ssh = chilkat.Ssh.new()

local sshPort = 22
local success = ssh:connect("ssh.example.com", sshPort)
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:open_session_channel()
if channelNum < 0 then
    print(ssh.last_error_text)
    return
end

-- Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
-- raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
-- echo typed commands back, and skips interactive login scripts.  The output is therefore
-- clean and easily parseable -- but because no prompt is ever sent, code must not wait for
-- one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
success = ssh:send_req_shell(channelNum)
if not success then
    print(ssh.last_error_text)
    return
end

-- There is no prompt to wait for, so make the command itself announce when it has finished
-- by echoing a marker after it.
success = ssh:channel_send_string(channelNum, "ls -l /tmp; echo DONE_MARKER\n", "utf-8")
if not success 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

-- Receive until the marker appears in the output.
local caseSensitive = false
success = ssh:channel_receive_until_match(channelNum, "DONE_MARKER", "utf-8", caseSensitive)
if not success then
    print(ssh.last_error_text)
    return
end

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

print(output)

ssh:disconnect()