thread-safe UUID generator

uuid_test.lua

local uuid = require 'uuid' -- From https://github.com/Tieske/uuid
local socket = require 'socket'

-- Get a unique seed
local seed, fh, err
for i = 1, 256 do
  seed = socket:gettime()*10000
  local filepath = ('/tmp/%s.uuid'):format(seed)
  fh, err = io.open(filepath)
  if fh then
    print(('SEED: %s taken. Keep trying...'):format(seed))
  else
    fh, err = io.open(filepath, 'a+')
    if fh then
      fh:write '.'
      fh:close()
      fh, err = io.open(filepath)
      if fh then
        local stamp = fh:read '*all'
        if stamp == '.' then
          break
        else
          print(('SEED: %s taken. Keep trying...'):format(seed))
        end
      else
        print(('FATAL: %s. Keep trying...'):format(err))
      end
    else
      print(('FATAL: %s. Keep trying...'):format(err))
    end
  end
  -- reset seed
  seed = nil
end

-- Validate seed
if seed == nil then
  error 'FATAL: Unable to get a unique seed'
end

-- Seeds the generator
uuid.randomseed(seed)

print(("SEED: %s | UUID: %s"):format(seed, uuid()))