title: Why doesn't the echo "Hello World!" statement work as expected?
body: <p>I'm learning the fundamentals of Bash scripting. If I am not mistaken, strings with no delimitations and delimited by double quotes (<code>"</code>) are interpreted almost in the same way and so, as alphanumeric strings; variables inside them are expanded. On the other side, strings delimited by single quotes (<code>'</code>) don't expand variables, and this is the main difference comparing them with the previuosly mentioned ones.
  Practicing a bit with the terminal, I noticed that one statement doesn't work as I expected. As you can see in this example:</p>
  
  <pre><code>MacBook-Pro-di-Rodolfo:~ Rodolfo$ echo Hello World!
  Hello World!
  MacBook-Pro-di-Rodolfo:~ Rodolfo$ echo 'Hello World!'
  Hello World!
  MacBook-Pro-di-Rodolfo:~ Rodolfo$ echo "Hello World!"
  echo "Hello World"
  Hello World
  </code></pre>
  
  <p>the last statement doesn't print out the same string as the previous ones, truncating the exclamation mark. Can anyone explain me the reason of this character removal?
  If it can be useful, I am running all this under Mac OS X v. 10.9.</p>