Lua cmd-line string

Question

Say I call Lua with this cmd:

luajit neuralnetwork.lua --satEpoch "somestring" --maxEpoch 50

How can I access this same cmd-line string from Lua?

I know about the arg table, but it removes all quotes from the original command string making it difficult to reconstruct:

{
   "--maxEpoch"
   "--satEpoch"
   "50"
   "somestring"
   [-1] : "luajit"
   [0] : "examples/neuralnetwork.lua"
}

If I can save the exact string to a file from within Lua, I can easily call it again later.

Answer 1

@peterpi is correct that the shell is interpreting the command and as a result stripping away the quotes. However, reconstructing the command exactly is not really necessary to have the shell interpret the command the same way as before.

For simple cases concatenating the arguments to the script is often enough:

local command = table.concat(arg, ' ', -1, #arg)

This will fail if the quotes are actually necessary, most commonly when an argument contains a space or shell character, so quoting everything is easy and somewhat more robust, but not pretty.

Here is an example with a Lua pattern to check for special (bash) shell characters and spaces to decide if and which quotes are necessary. It may not be complete but it handles filenames, most strings, and numbers as arguments.

local mod_arg = { }
for k, v in pairs(arg) do
    if v:find"'" then
      mod_arg[k] = '"'..v..'"'
    elseif v:find'[%s$`><|#]' then
      mod_arg[k] = "'"..v.."'"         
    else
      mod_arg[k] = v
    end
end 
local command = table.concat(mod_arg, ' ', -1, #mod_arg)
print(command)