Bash Coding Guidelines and Best Practices

Code Style

Always indent by four spaces, do not use tab characters.
Ensure lines do not end with white space characters (enable automatic line trimming in your editor of choice)
Place the keywords then / do on the same line like if / for / while and not a separate line.
Always use $( myCommand ) instead of backticks `` myCommand `` to execute commands in subshells

Always use the local keyword when declaring variables within functions.
Prefer using lowercase variable names except when exporting them to environment. Otherwise unintentional clashes with existing environment variables, e.g. $USER, or $PATH may happen.
Prefer using the bash builtin double brackets test operator [[ ... ]] instead of the single bracket test operator. It supports glob/regex pattern matching and better handles testing of empty variables. See http://mywiki.wooledge.org/BashGuide/Practices#Bash_Tests

Try to limit the usage of subshells which are expensive in emulated environments such as Cygwin.
1. Use $PWD instead of $(pwd) to get the current path.
2. Avoid unnecessary cat, use command < file instead of cat file | command which is executed in a subshell.

Use #!/usr/bin/env bash instead of #!/bin/bash
Use \033 as escape sequence instead of \e to support MacOS
Use sed -E instead of sed -r to enable extended regular expressions on Linux and MacOS. See https://www.gnu.org/software/sed/manual/sed.html#Command_002dLine-Options