title: "Program Aborted" but didn't return error code
body: <p>Today when I checked the log of a script,
  I found a command(unrar) failed with ("Program Aborted") but no error reported，</p>
  
  <p>this is my script excerpt:</p>
  
  <pre><code>unrar ...|tail -10 &gt;&gt; unrar.log  #I found "Program Aborted" here
  
  if [[ "${?}" -ne "0" ]] 
  then 
      echo "[ERROR] unrar application failed with $? errorcode"
  else
      echo "[INFO] unrar application succeeded"
  </code></pre>
  
  <p>Is this due to something wrong with my script or the system itself?</p>