title: test fails with "argument expected" when comparing "("
body: <p>Can someone please explain why this command returns an error (on Solaris ksh):</p>
  
  <p><code>
  if [ "(" = "(" ]; then echo 1;fi;<br>
  ksh: test: argument expected
  </code></p>
  
  <p>The same using bash is OK, and echoes "1" as expected<br>
  Also, using [[ ]] is OK.</p>
  
  <p>The problem seems to be the first "("</p>