title: File globbing and matching numbers only
body: <p>In a bash script I need to verify that the user inputs actual numbers so I have thought the easiest way to make myself sure about that is implementing a <code>case</code>:</p>
  
  <pre><code>case $1 in
      [0-9]*)
      echo "It's ok"
      ;;
      *)
      echo "Ain't good!"
      exit 1
      ;;
  esac 
  </code></pre>
  
  <p>But I'm having hard time with file globbing because I can't find a way to demand the $1 value has to be numeric only. Or another way could be excluding all the alternatives:</p>
  
  <pre><code>case $1 in
      -*)
      echo "Can't be negative"
      exit 1
      ;;
      +*)
      echo "Must be unsigned"
      exit 1
      ;;
      *[a-zA-z]*)
      echo "Can't contain letters"
      exit 1
      ;;
  esac
  </code></pre>
  
  <p>The thing is in this case I should be able to block "special" chars like ! ? ^ = ( ) and so forth... I don't know how to acheive it. Please anyone give me a hint?</p>