These are resources I’ve found particularly useful on other sites. This page used to be called “Unidex”.

Awk

• Famous Awk One-Liners Explained (archived)—Peteris Krumins runs through an old list of one-line commands in Awk, explaining how each one works.

Bash

• BashFAQ on Greg’s Wiki (archived)—This is the best Bash resource on the web, presenting answers to common questions asked of the #bash IRC channel on Freenode. These articles and others on the wiki are essential reading for intermediate and advanced users.

• Bash Hackers Wiki (archived)—A worthy complement to Greg’s Wiki with a more encyclopedic or “reference” approach.

C

• ##c wiki (archived)—This is the C analogue to Greg’s wiki; a collection of high-quality resources and links for the C language, something of an oasis in a sea of misleading information.

• comp.lang.c Frequently Asked Questions (archived)—In-depth answers to questions often asked on the comp.lang.c newsgroup for the C programming language. While it’s definitely useful to answer specific questions, if you already know a little about C, you will learn a lot from just browsing the site. I wish all FAQ sites were a tenth this good.

Emacs

• Mastering Emacs (archived)—Great articles on Emacs usage. The beginners’ articles assume a fair bit of familiarity, but intermediate-to-advanced users should find this fascinating reading.

• Why Emacs? (archived)—Bozhidar Batsov presents a very readable article explaining his enthusiasm for the GNU Emacs text editor, with particular emphasis on comparison to its rival Vim.

Perl

• Modern Perl (archived)—An overview of modern Perl development practice; a successor to the O’Reilly “camel book”. Available to read online for free.

sed

• Famous Sed One-Liners Explained (archived)—Peteris Krumins runs through an old list of one-line commands in sed, explaining how each one works.

Unix

• cat-v (archived)—The late Uriel’s website takes the Unix philosophy to fanatical extremes, leaving no sacred cow unslain. You may not agree with everything here, but all of it is worth reading and considering. Of particular interest are the historical Unix man page archives (archived) and the “Considered Harmful” subsite’s section on software (archived).

Vi and Vim

• Vimcasts (archived)—Drew Neil makes superb high-quality screencasts on Vim usage. He focusses on migrating away from TextMate, which was a popular editor for macOS at the time. The first few screencasts in particular are highly recommended for beginners; if you are new to Vim and want to see what it can do, start here.

• Derek Wyatt’s Vim Tutorial Videos (archived)—Derek Wyatt is an enthusiastic and engaging screencast host. His screencasts are helpfully divided into sections by skill: Novice, Intermediate, and Advanced. Some of the videos are quite long, but all are worth watching.

• Vim Tips Wiki (archived)—This community wiki is good for users who have mastered the basics of the editor and are now looking to see what other tricks it can do. Tips range from specific editing tricks to more general advice on managing Vim configuration.

• “Your problem with Vim is that you don’t grok vi.” (archived)—A very in-depth answer to a Stack Overflow question explaining some usage patterns for vi, all of which are applicable to Vim.

• Seven Habits of Highly Effective Text Editing (archived)—Vim’s author Bram Moolenaar explains some general patterns for efficient editing. It is supposed to be suitable for any editor, but has a very heavy self-confessed bias towards Vim.

• The Vi/Ex Editor (archived)—Re-host of a venerable article for vi and ex usage by Walter Alan Zintz, originally published in UnixWorld Online. Very readable, with lots of examples.