curl
80+ tested curl examples: GET/POST/PUT/DELETE, headers, auth, cookies, uploads, redirects, retries, and scripting.
one-liners
Short, self-contained shell one-liners
Pipes and redirection
How | connects commands together, and how >, >>, 2>&1, and <() route data to and from files, other commands, and each other.
Bulk rename a batch of files
Rename many files at once with a plain bash loop, safely handling spaces and previewing changes before committing.
Find the largest files on disk
Locate what's actually eating your disk space, from a whole filesystem down to one directory.