How to exit a REPL from the command line - powershell

Question

I'm currently learning Lua and also learning how to work with CMD.
I know how to change a directory path and run my codes and files from that path
but what I don't know and I'm here to ask for is how to get out of a programming language REPL when you start it in CMD
For example to jump into the Lua REPL you should type:
lua53 (--like python3 for the Python language)
then you changed the CMD environment to a Lua compiler and can't access CMD commands such as
dir, cd, cls etc. and everytime when I need to access these commands I have to close the CMD window and open a new one.
Now can you guys tell me am I able to access CMD commands while in the Lua REPL? Or do I have to exit Lua first, and is there any command to exit a REPL?

Answer 1

I'd recommend EOF (Ctrl + D on Unix) rather than SIGKILL (Ctrl + C) because some REPLs (node and python) choose to ignore the latter (perhaps because it's often used for copying text?); python will just print KeyboardInterrupt whereas node will only exit if you press Ctrl + C twice (it will send a message telling you this the first time).
EOF (Ctrl + D) on the other hand immediately exists all REPLs I have used so far.
The Lua REPL stops immediately when it receives either EOF or SIGKILL, so you can use both here.
Edit: As Sowban points out, EOF apparently is entered as Ctrl + Z then Enter in powershell.

Answer 2

You could type ctrl c to exit the process that's running generally.

Answer 3

I suggest to write a REPL by yourself.
But be warned :-)
The main loop with a prompt and the interpreting and executing function/method is mostly the easiest part.
99.99999% is the errorhandling thing.
One of my earliest interpreter language is (A)REXX.
A REPL without any errorhandling is done with...
/* REXX have to start with a comment */
do forever
parse pull input
interpret input
end
Now Lua sandboxed to an _ENV with io and os library and a little bit of errorhandling...
#!/usr/bin/env -S readline-editor /usr/local/bin/lua
-- ^--SHEBANG for Linux --------------------------------------------------------------------------------------
-- interpreter.lua
-- Sandboxed to io and os
-- Lua 5.4 >>-because-> goto label <const> load()
--------------------------------------------------------------------------------------------------------------
local Lua = function(...)
-- Info about OS
io.write(("%s\n"):format(io.popen('uname -a'):read())):flush()
-- Global Setting
debug.setmetatable((1), {__index = math}) -- Add math library to number as methods (like string for strings)
os.setlocale('de_DE.UTF8')
os.setlocale('en_US.UTF8', 'time')
io.write(os.date("[%c]\n" .. ("%s\n"):format(os.setlocale():gsub("%;", "\n")))):flush()
-- io.write(("%s\n"):format(_VERSION)):flush()
-- Label for goto
::lua::
-- Local Setting
local args <const> = args or {...}
local Lua = Lua or true
local cmd = cmd or ""
--------------------------------------------------------------------------------------------------------------
local env <const> = env or setmetatable({os = os, io = io}, -- The _ENV for load()
{__call = function(self, ...)
local self, t = ({...})[1] or self, "" -- First argument becomes self if one
if ({...})[1] == "help" then self = getmetatable(({...})[2]).__index end -- Showing metamethod __index (table)
for k, v in pairs(self) do
t = t .. ("%s => %s\n"):format(k, v)
end
return t
end,
__index = {cg = collectgarbage,
gt = getmetatable,
pairs = pairs,
tn = tonumber,
ts = tostring,
_V = ("%s \27[1;" .. (31):random(36) .. "m(sandboxed)\27[0m"):format(_VERSION)},
__tostring = function(self) return self._V end}) -- end env
--------------------------------------------------------------------------------------------------------------
local prompt = prompt or setmetatable({}, {__tostring = function() return getmetatable(env).__index._V .. "> " end})
local name <const> = name or _VERSION
local result = result or true
--------------------------------------------------------------------------------------------------------------
while Lua do
io.write(tostring(prompt))
cmd = io.read() or 'quit'
if cmd == "quit" then Lua, result = true, true break end
Lua, result = pcall(load("return " .. cmd or false, name, "t", env))
if Lua and result then
io.write(("%s"):format(tostring(result)))
else
goto exception
end
end
--------------------------------------------------------------------------------------------------------------
-- Errorhandler
::exception::
io.write(("%s\n"):format("Exception"))
if not Lua or not result then
io.output(io.stderr)
io.write(("[%s][%s][%s]\n\27[1;31m>>-Exception->\27[0m %s\n"):format(os.date(), _VERSION, cmd, result)):flush()
io.output(io.stdout)
collectgarbage()
goto lua
end
goto lua
end
--------------------------------------------------------------------------------------------------------------
-- EXAMPLE ---------------------------------------------------------------------------------------------------
-- Lua = require("interpreter")
Lua() -- UNCOMMENT-> For direct execution like: /bin/lua interpreter.lua
return Lua -- UNCOMMENT-> For: Lua = require("interpreter")
Ctrl&C quits hardly
Ctrl&D is only an exception
...and os.exit(0) do an clean exit with returncode 0.
Impression