title: Confusing lua return codes from os.execute
body: <p>I'm trying to run the following code in sas:</p>
  <pre><code>proc lua restart;
  submit;
      local cmd = &quot;&amp;cmd.&quot;
      local ret_code = os.execute(cmd)
      sas.symput('ret_code', ret_code)
  endsubmit;
  run;
  </code></pre>
  <p>Macro variable <em>cmd</em> resolves to a command I want to run. When it is successful, i get return code equals to 1 (why not 0?). But when it's not, it resolves to a dot.</p>
  <p>I'm confused, why am i getting such strange return values? How to get 0 if everything's fine and &gt; 0 if something's wrong from lua script? I'm using linux os</p>