Funciones
pasando parámentros a funciones:
https://stackoverflow.com/questions/6212219/passing-parameters-to-a-bash-function
http://tldp.org/LDP/abs/html/complexfunct.html
variables locales en funciones:
http://tldp.org/LDP/abs/html/localvar.html
retorno de valores:
https://www.linuxjournal.com/content/return-values-bash-functions