''#!/usr/bin/env bash'' - Use ''bash'' found in the environment path. Protects against not knowing where user's ''bash'' is installed.

====== set options ======

''set options -xeuo''

Commonly used options:

  * ''-x'':  turns on debug output, logging each command as it is executed
  * ''-e'':  causes the script to exit on most command failures (non-zero exit codes)
  * ''-u'':  treats unset variables and parameters other than the special parameters @ or * as an error when performing parameter expansion
  * ''-o pipefail'': causes the script to exit if a command in a pipeline fails
  * use a + to unset them if necessary

Many more options available:  https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

====== Variables ======

  * ''$@'' - All of the arguments as individual strings
  * ''"$*"'' - All of the arguments as a single string
  * ''$#'' - The number of arguments
  * ''$1..n'' - Where n is an integer, the nth argument in the list
  * ''$0'' - The command name
  * ''$?'' - The last exit code
  * ''$IFS'' - Internal/input field separator (defaults to combo of space, newline and tab)

====== Functions ======

Declaring a function (needs to happen before use):

''function <function_name> { ... do things ... }''

- or -

''<function_name>() { ... do things ... }''

  * Nothing ever goes inside parentheses.
  * Passed parameters can be accessed with ''$1''..''$n''.

====== Tips ======

  * [[https://stackoverflow.com/a/16496491|Use getopts to parse commandline options]].