title: Why am I getting a 'unary operator expected' error?
body: <p>I'm writing a shell script to streamline my development workflow.</p>
  
  <p>It takes an argument as to which theme folder I'm going to be working in and starts <code>grunt watch</code> on that directory.</p>
  
  <p>If I call the script without the necessary argument I'm currently printing a warning that a theme needs to be specified as a command line argument.</p>
  
  <p>I'd like to print a list of the available options, e.g. theme directories</p>
  
  <p>This is what I have so far...</p>
  
  <pre><code>THEME=$1
  
  if [ $THEME == '' ]
  then
      echo 'Need to specify theme'
  else
      cd 'workspace/aws/ghost/'$THEME'/'
      grunt watch
  fi
  </code></pre>
  
  <p>Ideally I'd replace the output of the <code>echo</code> line with an <code>ls</code> of the themes parent directory like so</p>
  
  <pre><code>THEME=$1
  
  if [ $THEME == '' ]
  then
      echo 'Need to specify theme from the following'
      ls workspace/aws/ghost
  else
      cd 'workspace/aws/ghost/'$THEME'/'
      grunt watch
  fi
  </code></pre>
  
  <p>However this gives me the following error</p>
  
  <pre><code>./ghost_dev.sh: line 3: [: ==: unary operator expected
  </code></pre>