title: Check existence of input argument in a Bash shell script
body: <p>I need to check the existence of an input argument. I have the following script</p>
  
  <pre><code>if [ "$1" -gt "-1" ]
    then echo hi
  fi
  </code></pre>
  
  <p>I get</p>
  
  <pre><code>[: : integer expression expected
  </code></pre>
  
  <p>How do I check the input argument1 first to see if it exists?</p>