finding locations of many files via kpse

[Erik Nijenhuis]

Hi Karl,

On Mon, 2024-08-05 at 14:18 -0600, Karl Berry wrote:
> Specifically, I used getopt_long_only pervasively throughout the TeX
> engines, drivers, etc., back when I unified option handling among the
> programs extant in the late 1980s. Programs added since then sometimes
> use getopt_long_only, sometimes not. We use the Perl equivalent of
> getopt_long_only in tlmgr and install-tl.
Thanks, that clarifies a lot!

> I don't know what you mean. lua-alt-getopt was an early Lua option
> parsing package written independently by Aleksey Cheusov (and not
> updated since 2010). It's not used within TL as far as I know.
> Grepping in a bindir, I see that luaotfload-tool uses it, and, so far as
> that grep showed, nothing else.
Because it would be nice if there's a utility which makes it easy and consistent
for anyone who would want to create a CLI in LuaTeX. However, the script I
mentioned doesn't support `getopt_long_only` after some investigation
unfortunately...

> Me too. That's why I used it. At some point I had to copy the source
> files into TL (kpathsea/getopt*) because of incompatibilities, but it's
> still GNU getopt.
> 
>     However, from a historical standpoint, the alternative getopt
>     library within TeX Live should be favored instead,
> 
> I'm not aware of any "alternative library" in TL (for C).
Thanks for clarifying. With alternative library I meant the getopt files in TL.
Didn't know it's an exact copy of GNU getopt.

So to follow up on Norbert's synopsis, it could be something like:
```lua
local function parse_opts(args)
  local options = {
    mark_sys_files = false,
    progname = "lualatex"
  }
  local remaining_args = {}
  local i = 1
  while i <= #args do
    local arg = args[i]
    if arg:match("^%-%-?mark%-sys%-files$") then
      options.mark_sys_files = true
    elseif arg:match("^%-?%-?progname=") then
      options.progname = arg:match("^%-?%-?progname=(.*)")
    elseif arg:match("^%-?%-?progname$") then
      i = i + 1
      if i <= #args then
        options.progname = args[i]
      else
        error("Option 'progname' requires an argument")
      end
    else
      table.insert(remaining_args, arg)
    end
    i = i + 1
  end
  return options, remaining_args
end

local function parse_args(args)
  local options, remaining_args = parse_opts(args)

  if #remaining_args == 0 then
    error("Expected subdir argument")
  end

  local subdir = remaining_args[1]

  return options, subdir
end

local options, subdir = parse_args(arg)

if options.mark_sys_files then
  print("System files will be marked.")
else
  print("System files will not be marked.")
end

print("Program name:", options.progname)
print("Subdirectory:", subdir)
```

This would then work for the following cases:
```bash
texlua norbert-search.lua --mark-sys-files --progname=myprogram subdir
texlua norbert-search.lua --mark-sys-files --progname myprogram subdir
texlua norbert-search.lua -mark-sys-files -progname=myprogram subdir
texlua norbert-search.lua -mark-sys-files -progname myprogram subdir
```
Although, subdir might be an option as well and by default the cwd.


Best, Erik