---
title: Developer Cheat Sheets: Regex, jq, Ports, Subnets | Relic
description: Compact, accurate cheat sheets for regex, jq, JSONPath, subnetting, ports and key formats. The syntax you look up every few weeks, all in one place.
canonical: https://relic.space/blog/topics/dev-reference
source: https://relic.space/llms.txt
---
Topic

# Cheat sheets for the syntax you half-remember

Nobody memorizes regex flavors, jq filters or subnet masks. You look them up, every time. These cheat sheets keep the lookup short: the forms you actually use, correct and copy-ready, with just enough explanation to trust them.

Start here

[Pillar·10 minRegex cheat sheetThe regex pieces you actually reach for, character classes through lookarounds, with the flavor differences that bite you and a handful of patterns worth saving.Read ](https://relic.space/blog/regex-cheat-sheet)

In this topic

[9 minHow to copy and paste in Vimy copies and p pastes, but only inside Vim. How registers work, how to reach the system clipboard when your build says -clipboard, and how to copy out over SSH and in tmux.Read ](https://relic.space/blog/how-to-copy-and-paste-in-vim)[8 minHow to copy to the clipboard from the command linePipe any command into the clipboard on Mac, Linux, Windows and WSL. The commands for each, plus the newline and encoding problems that break pasted text.Read ](https://relic.space/blog/copy-to-clipboard-from-the-command-line)[9 minWhat AI crawlers fetch from a small open-source site: 31 days of logsWe checked every request that claimed to be GPTBot, ClaudeBot, PerplexityBot and the rest against the operators' published IP lists. Then we looked at what the real ones read. The data is downloadable.Read ](https://relic.space/blog/ai-crawlers-on-a-small-site)[7 minJSONPath examplesJSONPath is XPath for JSON. One small store document, threaded through wildcards, slices, filters and recursive descent, with the honest note on how implementations vary.Read ](https://relic.space/blog/jsonpath-examples)[7 minjq cheat sheetjq is sed for JSON. The filters you use most, built up against one API response so every command has a visible result, from map and select to group\_by and raw output.Read ](https://relic.space/blog/jq-cheat-sheet)[7 minwget vs curl: what is the difference?wget and curl both fetch over HTTP, and there the resemblance ends. One is a recursive downloader, the other a protocol swiss army knife. What each is genuinely better at.Read ](https://relic.space/blog/wget-vs-curl)[5 minSubnet cheat sheetThe prefix length tells you how many addresses a block holds and how many you can assign. The full /8 to /32 table, the reserved ranges, and the math to find a network and broadcast by hand.Read ](https://relic.space/blog/subnet-cheat-sheet)[5 minPort numbers listThe ports people actually look up, grouped by use, each with the protocol that matters and what runs there. Web, mail, file and shell, databases, infrastructure, and local dev ports.Read ](https://relic.space/blog/port-numbers-list)[5 minEd25519 vs RSAFor a new SSH or signing key, Ed25519 is the better default: smaller, faster, and harder to misconfigure. When RSA is still the right call, and the commands to generate each.Read ](https://relic.space/blog/ed25519-vs-rsa)[6 minTOML vs YAMLTOML aims to be obvious and minimal; YAML serializes any data a human can read. The same config in both, YAML's sharp edges stated accurately, and where each one won.Read ](https://relic.space/blog/toml-vs-yaml)