====== Shell- und Umgebungsvariablen  ======
  variable=42
  bash -c 'echo $variable'
  export variable
  bash -c 'echo $variable'

  echo 'export variable1=23' >> /etc/profile
  echo 'export variable2=23' >> ~/.bashrc

  echo 'export variable3=23' >> ~/.bash_profile

  export variable=23
  env | grep ^variable

====== Links ======
  * http://tldp.org/LDP/abs/html/variables.html
  * http://tldp.org/LDP/abs/html/variables2.html