Surprisingly, https://learnxinyminutes.com/docs/bash/ https://learnxinyminutes.com/docs/bash/ is the best resource out there to learn shell scripting. This page

Surprisingly, https://learnxinyminutes.com/docs/bash/ https://learnxinyminutes.com/docs/bash/ is the best resource out there to learn shell scripting. This page basically turned me from a novice who could only write two commands with | or && between them to a competent shell programmer. My shell scripts have functions, descriptive variables, error handling, good formatting, etc.