title: Command not found in Bash's IF-ELSE condition when using [! -d "$DIR"]
body: <p>I have a code like this </p>
  
  <pre><code>#!/bin/bash 
  DIR="test_dir/";
  if [! -d "$DIR"]; then
      # If it doesn't create it
      mkdir $DIR
  fi
  </code></pre>
  
  <p>But why executing it gave me this:</p>
  
  <pre><code>./mycode.sh: line 16: [!: command not found
  </code></pre>
  
  <p>What's the right way to do it?</p>