PHP

Recursive Directory Walker

Yield every file under a directory using a generator and SPL's RecursiveIteratorIterator. Filter by extension or any other predicate without slurping all paths into memory first.

1h ago 0

Go

Signal Handling with signal.NotifyContext

Go 1.16+ `signal.NotifyContext` returns a context that's canceled on the listed signals. Cleaner than the legacy `signal.Notify(channel)` dance for graceful shutdown.

1h ago 0

SQL

LATERAL Join — Per-Row Subquery

PostgreSQL `LATERAL` lets a join's right-hand side reference the left-hand row — like a correlated subquery, but supplying multiple columns or rows. Perfect for "top-N per group".

1h ago 0

Kotlin

async / await for Parallel Results

`async` returns a `Deferred<T>` — like a Future. Use it when you need a RESULT back, in parallel. Call `.await()` to get the value (suspends until ready).

1h ago 0

Bash

Parallel Map with xargs -P

`xargs -P N` is a Swiss-army knife for parallel map: feed it a list of inputs and a command, it runs N workers. Faster and simpler than bash for-loops with `&`.

1h ago 0

Bash

Kill Process by Port

When a port is "already in use" — find the offending process and (carefully) kill it. `lsof` is the gold standard; `ss` is the lighter modern alternative.

1h ago 0

Rust

Group By a Key (fold into HashMap)

No built-in `group_by`, but `fold` into a `HashMap` does the same thing in two lines — and the type system tracks keys / values correctly.

1h ago 0

SQL

UPDATE with JOIN

Update one table using values from another. Syntax varies by database — PostgreSQL uses `FROM`, MySQL puts the join in the `UPDATE` clause.

1h ago 0

Rust

Clone vs Copy — When to Use Each

Stack-allocated primitives implement `Copy` (auto-duplicated). Heap-owning types like `String` and `Vec` only implement `Clone` (you must explicitly call `.clone()` to opt into the deep copy cost).

1h ago 0

Bash

Word Frequency Count

Classic shell one-liner: split text into words, sort, count uniques, sort by count. Useful for log analysis, content audits, and tag-cloud-style summaries.

1h ago 0

Go

Struct Embedding (Composition over Inheritance)

Go has no inheritance. Embed a type to "promote" its fields and methods as if they were on the outer type. Same effect as inheritance for most purposes, but explicit.

1h ago 0

Go

strconv — String ↔ Number Conversions

`strconv.Atoi` / `Itoa` for the common int<->string case; `ParseFloat`, `ParseBool`, `Quote` for everything else. Always handle the error — strings can be anything.

1h ago 0

Bash

Trap Signals for Cleanup

Use `trap` to delete temp files / kill background workers when the script exits — even on Ctrl-C or an unhandled error. Single most-undervalued bash feature.

1h ago 0

Bash

Run Command with Timeout

`timeout` (GNU coreutils) kills a command after N seconds. Returns exit code 124 on timeout — let the caller distinguish "timed out" from "failed for other reasons."

1h ago 0

Go

strings.Builder — Efficient Concatenation

Building strings with `+` allocates O(n²) memory. `strings.Builder` writes to an internal buffer with a single final allocation — orders of magnitude faster in loops.

1h ago 0

HTML

Progress and Meter Elements

`<progress>` shows how much of a task is done (downloads, multi-step forms). `<meter>` shows a value within a known range (disk usage, password strength). Both render as native UI in every browser.

1h ago 0

Python

functools.cache Memoization

Wrap any pure function with @cache (Python 3.9+) and get an unbounded memoization layer for free. Use @lru_cache(maxsize=N) when you need a bounded cache.

1h ago 0

Rust

Unit Tests with #[test] and assert_eq!

Tests live alongside the code they test. `cargo test` runs every `#[test]` function. Use `#[cfg(test)] mod tests` so the test code is compiled out of release builds.

1h ago 0

Python

Result / Either with Generics

Encode "this might fail" in the type signature instead of throwing. Python 3.12+ generics syntax keeps it compact. Forces the caller to handle the failure branch.

1h ago 0

Kotlin

Room — Android Database

Room is the official Android persistence library — annotation-driven, compile-time SQL verification, coroutine + Flow integration out of the box.

1h ago 0

TypeScript

User-Defined Type Guards

When TypeScript can't narrow a union for you, write a `x is T` predicate. Inside any block where the guard returns true, the compiler knows the narrower type.

1h ago 0

Kotlin

Data Classes — Records Done Right

`data class` auto-generates `equals`, `hashCode`, `toString`, `copy`, and `componentN` (destructuring). Replaces boilerplate POJOs / Records / classes-with-lombok in one line.

1h ago 0

Rust

Concurrency Limit with Semaphore

Fan out N tasks but limit how many run at once via `tokio::sync::Semaphore`. Standard pattern for HTTP fan-out where you must respect a server's rate limit.

1h ago 0

Go

Generic Set Type

A type-safe Set built on `map[T]struct{}` and Go generics. Has Add / Has / Delete / Size — and uses zero bytes per entry for the value side.

1h ago 0

Go

log/slog — Structured Logging

`log/slog` (Go 1.21+) is the standard structured logger. Drop-in replacement for `log` with key/value attributes and JSON output for log-pipeline ingestion.

1h ago 0

TypeScript

Truncate at Word Boundary

Cap a string at `max` characters without splitting a word, appending an ellipsis when truncated. Falls back gracefully if the last word is longer than `max`.

1h ago 0

Go

goroutine + sync.WaitGroup

`go fn()` spawns a goroutine. To wait for several to finish, use `sync.WaitGroup` — call `Add` before spawning, `Done` (deferred) inside, `Wait` to block until all are done.

1h ago 0

Java

Singleton via enum

`enum` with a single value is the simplest correct singleton implementation: lazy, thread-safe, serialization-safe, reflection-safe. Joshua Bloch's recommendation in Effective Java.

1h ago 0

PHP

Pluralize / Singularize (English basics)

A pragmatic rule-based English pluralizer covering the common cases (s, es, ies, irregular nouns). Not perfect, but good enough for UI labels like "1 item" / "3 items".

1h ago 0

PHP

Human-Readable "Time Ago"

Convert a timestamp into a short relative phrase: "just now", "5 minutes ago", "3 days ago". Falls back to an absolute date once the delta exceeds a year.

1h ago 0