title: Check whether two files exist (in shell script)
body: <p>I'm writing a shell script and trying to check whether two files exists. 
  Here is the script example:</p>
  
  <pre><code>#!/bin/bash
  
  if [[ [ -e File1Name ] -a [ -e File2Name ] ]]
  then
    echo Yes
  el
    echo No
  fi
  </code></pre>
  
  <p>and get</p>
  
  <pre><code>script: line 5: conditional binary operator expected
  script: line 5: syntax error near `-e'
  script: line 5: `if [[ [ -e CA ] -a [ -e CA-draw ] ]]'
  </code></pre>
  
  <p>What is wrong with my script and hot to fix it?</p>