Pillar·9 min
Regex cheat sheet
The regex pieces you actually reach for, character classes through lookarounds, with the flavor differences that bite you and a handful of patterns worth saving.
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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.
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8 min
JSONPath examples
JSONPath is XPath for JSON. One small store document, threaded through wildcards, slices, filters and recursive descent, with the honest note on how implementations vary.
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jq cheat sheet
jq 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.
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wget 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.
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Subnet cheat sheet
The 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.
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Port numbers list
The 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.
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Ed25519 vs RSA
For 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.
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TOML vs YAML
TOML 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.
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