Lua

Get Text Received on the SSH stderr Buffer

Demonstrates the Chilkat Ssh.GetReceivedStderrText method, which decodes and returns the text accumulated in a channel's separate stderr buffer. The first argument is the channel number and the second is the charset. The stderr buffer is cleared after the text is returned.

Background: This is only meaningful when StderrToStdout is false, which keeps error output in its own buffer instead of merging it into the normal receive buffer. Separating the two lets a program parse a command's real output cleanly while still capturing diagnostics — important because many Unix tools write warnings to stderr that would otherwise corrupt the parsed result. With merging enabled, this buffer stays empty and the text appears via GetReceivedText instead.

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Lua

local chilkat = require("chilkat")

-- Demonstrates the Ssh.GetReceivedStderrText method, which decodes and returns the text in a
-- channel's separate stderr buffer.  The 1st argument is the channel number and the 2nd is the
-- charset.  The stderr buffer is cleared after the text is returned.

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

-- Keep stderr in its own buffer rather than merging it into the normal receive buffer.
ssh.stderr_to_stdout = false

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

-- Run a command that writes to both stdout and stderr.
success = ssh:send_req_exec(channelNum, "ls /etc/hosts /no/such/path")
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

success = ssh:channel_receive_to_close(channelNum)
if not success then
    print(ssh.last_error_text)
    return
end

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

print("STDOUT: " .. stdoutText)

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

print("STDERR: " .. stderrText)

ssh:disconnect()