one_line_fn_call.rb

tmp_file_path('gateway', '/data/nginx_tmp')

tmp_file_path.rb

require 'fcntl'

def tmp_file_path(prefix, base_path)
  while true
    random_string = prefix + Array.new(16) { rand(256) }.pack('C*').unpack('H*').first
    begin
      fh = File.open(File.join(base_path, random_string), Fcntl::O_EXCL | Fcntl::O_CREAT | Fcntl::O_WRONLY)
      fh.close
      return File.join(base_path, random_string)
    rescue Errno::EEXIST
    end
  end
end