Bash

Read File Line-By-Line (the safe way)

The classic `for line in $(cat file)` is wrong — it word-splits and globbing fires on filenames. Use `while IFS= read -r line` with input redirection.

44m ago 0

JavaScript

Random Hex Color

Generates a random 6-digit hex colour string. Useful for seeding avatar backgrounds, chart series colours, placeholder UI elements, and testing colour-dependent components. The crypto version produces a more unpredictable result suitable for generating unique palette tokens.

44m ago 0

Rust

String vs &str — The Cheat Sheet

`String` is an owned, growable heap allocation; `&str` is a borrowed view into a UTF-8 buffer. Function params should usually take `&str`; return types use `String` when ownership is needed.

44m ago 0

Bash

Create User With Sensible Defaults

Provision a new user account with a home directory, default shell, and sudo membership. Idempotent — re-running on an existing user is a no-op.

44m ago 0

Python

Safe JSON Read/Write

Idiomatic helpers for reading + writing JSON to disk, with atomic writes and pretty-printed output. Catches the common "edit and save → corrupt file on crash" failure mode.

44m ago 0

JavaScript

Promise All with Concurrency Limit

Runs an array of async tasks with a maximum concurrency cap, preventing you from firing hundreds of requests simultaneously. Processes items in batches, moving to the next as slots free up. Essential when hitting rate-limited APIs or processing large datasets without overwhelming the server.

44m ago 0

PHP

Partition Array Into Two Buckets

Split an array into [matches, non-matches] using a predicate callback. Single pass, preserves order, returns two lists.

44m ago 0

Go

time.Ticker — Periodic Tasks

`time.NewTicker(d)` fires on a channel every `d` interval. Combine with select + a done channel for a clean way to run periodic work that can be cancelled.

44m ago 0

Bash

Sum a Column with awk

Awk's default field splitter is whitespace; pass a single character with -F. Perfect for summing the Nth column of a log file or CSV.

44m ago 0

TypeScript

Environment Variable Validator

Validate process.env at boot-time and exit fast if anything's missing. The returned object is typed so the rest of the code reads `env.DATABASE_URL` instead of `process.env.DATABASE_URL!`.

44m ago 0

TypeScript

invariant() — Always-On Assertion

Throw if a condition is false, with TypeScript narrowing the type afterwards. Replaces ad-hoc `if (!x) throw` ladders and gives you type-safe guards in one line.

44m ago 0

Go

Custom Generic Constraints

Type constraints are interfaces with type sets. Use them to express "any numeric" or "any ordered" without resorting to `any`.

44m ago 0

TypeScript

Chunk Array Into Fixed-Size Pieces

Split an array into chunks of `size` items. Common building block for batch APIs — "send 50 rows per request" — and for paginated grids.

44m ago 0

Rust

Result Combinators + the ? Operator

`Result<T, E>` chains like `Option`. The `?` operator unwraps `Ok` or early-returns the `Err`, converting via `From` so callers can use one error type for many sources.

44m ago 0

PHP

Slack Incoming-Webhook Notification

Fire a quick notification to a Slack channel via an incoming webhook URL. Includes basic markdown-style mentions and an attachment color for severity.

44m ago 0

Java

Stream Basics — filter / map / collect

The fluent pipeline for transforming collections. `filter` keeps matching elements, `map` transforms each one, `collect(toList())` materializes the result.

44m ago 0

Kotlin

Star Projections (List<*>, etc.)

`List<*>` means "list of something I don't need to know exactly" — read-only with Any? as element type. Useful when you genuinely don't care about the parameter.

44m ago 0

HTML

Skip-to-Main-Content Link

Keyboard users (and screen-reader users) tab through every nav link before reaching content. A skip-link as the first focusable element jumps straight to <main>. Required for WCAG 2.1 AA.

44m ago 0

Python

chunked — Split Iterable into Fixed-Size Pieces

Lazy chunker that works on any iterable, not just lists. Common building block for batch APIs — "send 50 rows per request" — without loading the source into memory.

44m ago 0

Bash

Unique While Preserving Order

`sort -u` re-orders. `awk '!seen[$0]++'` is the classic order-preserving dedupe — and it's a single line.

44m ago 0

TypeScript

URL Builder with Type-Safe Query

Build URLs with a clean query-param API. Skips null/undefined automatically, encodes everything, and accepts arrays for repeated keys. Avoids manual string concatenation.

44m ago 0

Bash

SSH to Multiple Hosts in Parallel

Run the same command on a fleet of hosts. Three patterns: serial loop (simplest), GNU parallel (fastest), pssh (purpose-built).

44m ago 0

Kotlin

fold and scan

`fold` accumulates from a seed across all items. `runningFold` / `scan` yields every intermediate accumulator value — running totals, cumulative metrics.

44m ago 0

SQL

Views and Materialized Views

A view is a named query — no data stored. A materialized view caches the result; refresh it on demand. Great for expensive joins or aggregations that don't need to be real-time.

44m ago 0

Java

Optional Chains — flatMap, filter

`flatMap` lets you chain Optional-returning methods without nested `if`. `filter` short-circuits to empty if the predicate fails. The functional equivalent of safe-navigation `?.`.

44m ago 0

Python

take / drop / takewhile

Take the first N items of an iterable (or while a predicate holds). drop is the complement. Lazy via islice + itertools.dropwhile — works on infinite generators.

44m ago 0

Go

Read File — Whole / Lines / Bytes

Three common patterns: load it all (`os.ReadFile`), iterate line-by-line with `bufio.Scanner`, or stream chunks via `io.Reader`. Pick by file size.

44m ago 0

Bash

Sort by a Specific Column

Sort takes -k for column-based ordering and -t to set the delimiter. -h sorts human-readable sizes ("1.5G", "300K") correctly.

44m ago 0

SQL

EXISTS vs IN — Subquery Filtering

Both check membership. `EXISTS` is usually faster for big subqueries (stops at first hit). `IN` is more readable for small fixed lists. `NOT IN` is dangerous with NULLs — prefer `NOT EXISTS`.

44m ago 0

Kotlin

Cheatsheet: let / apply / also / run / with

Five scope functions cover ~95% of "do something with x" patterns. Pick by two axes: receiver (this vs it) and return value (object itself vs block result).

44m ago 0