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The goal of this book is to document commonly-known and lesser-known methods of doing various tasks using only built-in bash features. Using the snippets from this bible can help remove unneeded dependencies from scripts and in most cases make them faster.

I learned about this via Can anyone suggest me good Bash book filled with small examples only? : r/bash.

Other recommendations in that thread:

• BashGuide - Greg's Wiki
• Advanced Bash-Scripting Guide (note: there are comments that warn people away from this guide because it has errors that the author won't respond to)