Dictionaries in bash scripts - it is possible

Here is something new I learned. Modern unix shells like bash (>4.x) or zsh, offer associative arrays, sometimes called maps, or dictionaries (in Python).

In the past, I worked on legacy systems (RHEL4,5) series which offered BASH 3.x, where this didn't exist, and since then I do most of my programming in Python. Never the less, it was a pleasant surprise to find this after the first quarter of the bash man page:

   Bash  provides  one-dimensional  indexed and associative array variables. 
   ...
   Associative arrays are created using declare -A name.

Here is an example:

$ declare -A aa
$ aa[hello]=world
$ echo ${aa[hello]} 
world
$ aa[hello world]="from bash"
$ echo ${aa[hello world]} 
from bash

You can read more about this in your nearest man bash.