Lua

SSH Exec (Execute Command Line)

Demonstrates running a single command on an SSH server with an exec request and retrieving its output. The example connects, authenticates, opens a session channel, sends the command, reads until the server closes the channel, and then checks the exit status.

Background: exec is the workhorse of SSH automation: it runs one command and the server closes the channel when the command exits, which is a definitive end-of-output signal. No PTY is involved, so the shell runs non-interactively — no prompt, no echoed input, no ANSI escape codes — giving clean, parseable output. Remember that an accepted exec request only means the request was accepted; the command's own success is reported through the channel exit status. Command syntax depends on the remote shell, which is the user's default shell on Linux/UNIX and usually CMD.EXE on Windows SSH servers.

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Lua

local chilkat = require("chilkat")

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

-- Demonstrates running a single command on an SSH server with an exec request and retrieving
-- its output.  An exec request runs one command and the server closes the channel when it
-- finishes -- no PTY and no shell prompt are involved, so the output is clean and parseable.

local ssh = chilkat.Ssh.new()

-- The hostname may be a hostname or an IP address.
local hostname = "ssh.example.com"
local port = 22
local success = ssh:connect(hostname, 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

-- Open a session channel.  Several session channels may be open at once on one connection.
local channelNum = ssh:open_session_channel()
if channelNum < 0 then
    print(ssh.last_error_text)
    return
end

-- The command syntax depends on the remote system's shell.  On Linux/UNIX it is typically the
-- user's default shell; on Windows SSH servers it is usually CMD.EXE.
--   Linux/UNIX:  "ls -l /tmp"        or  "cd /etc; ls -la"
--   Windows:     "dir"               or  "\"cd \\temp&&dir\""
success = ssh:send_req_exec(channelNum, "ls -l /tmp")
if not success then
    print(ssh.last_error_text)
    return
end

-- IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
-- it, this call waits forever if the server never sends channel close.
ssh.read_timeout_ms = 15000

-- Read the output until the server sends channel close, which happens when the command exits.
success = ssh:channel_receive_to_close(channelNum)
if not success then
    print(ssh.last_error_text)
    return
end

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

print(cmdOutput)

-- An accepted exec request does not mean the command succeeded.  Check the exit status.
if ssh:channel_received_exit_status(channelNum) then
    print("Exit status: " .. ssh:get_channel_exit_status(channelNum))
end

ssh:disconnect()