Bash bits, nibbles and bytes: Handling command line arguments
There are plenty of tutorials out on the web but they tend to shove a whole lot down your throat in one big hard to swallow gob. I intend to make short, sharp and shiny snippets so it is easy to understand and use.
To make a flexible bash script you need the ability to pass arguments to the script. This allows the script to handle different data or even do different things according to how it is called. Bash assigns each argument a number from "$1" to "$n" and the total number of arguments is represented by "$#". Now while you can access each argument directly by number you can never be sure whether all arguments are in the correct order or the correct number of arguments have been given. The best way is to process each argument on a case by case basis and be independent of the order and number of arguments.
While that sounds complicated to do it is actually quite simple with a little loopy logic and a case by case comparison. In other words a "while" loop and a "case" structure is enough to handle our needs. Here is an example:-
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