title: How to represent multiple conditions in a shell if statement?
body: <p>I want to represent multiple conditions like this:</p>
  <pre><code>if [ ( $g -eq 1 -a &quot;$c&quot; = &quot;123&quot; ) -o ( $g -eq 2 -a &quot;$c&quot; = &quot;456&quot; ) ]   
  then  
      echo abc;  
  else  
      echo efg;   
  fi  
  </code></pre>
  <p>but when I execute the script, it shows</p>
  <pre class="lang-none prettyprint-override"><code>syntax error at line 15: `[' unexpected,
  </code></pre>
  <p>where line 15 is the one showing if ....</p>
  <p>What is wrong with this condition? I guess something is wrong with the <code>()</code>.</p>