title: Does os.execute block thread in lua?
body: <p>In my nginx+lua app OS executing a command line something like <code>os.execute("ls 2&gt;&amp;1 | tee a.txt")</code>
  I want to know does it block main app? I want use command "execute-and-forgot" case. If it blocks how to fix it and execute a simple line in background thread?</p>