Bash

History

Ctrl+R will open the search history window.
You may now use Ctrl+R again to search for the previous match.

Edit current line in EDITOR

Ctrl-X, Ctrl-E: will open the current line in EDITOR.

Arrays

    arr=(1 2 3)
    echo ${arr[0]}
    echo ${arr[@]}
    echo ${arr[*]}
    echo ...