Tags
#php
#kotlin
#bash
#go
#sql
#rust
#typescript
#html
#java
#python
#files
#utils
#strings
#http
#concurrency
#async
#json
#arrays
#security
#types
#crypto
#database
#dates
#format
Bash
flock — Cron-Singleton Lock
Prevent two copies of a cron job from running simultaneously. flock takes an FD to a lock file; if the lock is held, the second invocation exits immediately.
@admin
Python
Generate Strong Random Password
Build a password using the `secrets` module (CSPRNG) with rejection sampling for unbiased distribution. Use this — NOT random.choice, which is seeded predictably.
Python
Async Context Manager (aiohttp pattern)
Define an async resource using `@asynccontextmanager` from contextlib. Cleaner than writing a class with __aenter__/__aexit__ for one-off wrappers.
PHP
Haversine Distance Between Two Coordinates
Compute the great-circle distance between two latitude/longitude points using the haversine formula. Returns kilometers; multiply by 0.621 for miles. Useful for "stores near me" features.
PHP
Paginated Query Helper
Run a SELECT with LIMIT/OFFSET and also return the total row count, so you can render "Page 3 of 47" UIs. Single function, two round trips.
PHP
PDO Transaction Wrapper
Run a closure inside a transaction. Commits on success, rolls back on any exception, then re-throws so the caller can react. Avoids the bug-prone copy-paste of begin/commit/rollBack.
Kotlin
Operator Overloading
Specially-named methods or extensions get operator syntax: `plus → +`, `minus → -`, `times → *`, `get → []`, `invoke → ()`, `contains → in`. Use sparingly for types that have natural arithmetic semantics.
HTML
Login Form (with autocomplete hints)
A complete login form with the autocomplete attributes that browsers + password managers depend on. Missing these causes 1Password, Bitwarden, and Chrome to mis-detect the form.
SQL
Pagination with LIMIT / OFFSET
`LIMIT N OFFSET M` is universal — but degrades on deep pages (the DB still has to scan past M rows). Keyset (cursor) pagination is much faster for huge tables.
SQL
Pattern Matching — LIKE / ILIKE / SIMILAR
`LIKE` uses `%` (any string) and `_` (single char). PostgreSQL `ILIKE` is case-insensitive. For real regex, reach for `SIMILAR TO` (POSIX) or `~` (PostgreSQL).
Go
Generic Function with Type Parameters
Go 1.18+ generics. `[T any]` is unconstrained; `[T comparable]` allows == and !=; custom constraints work too. The compiler infers T from arguments.
Rust
Iterator Chain — map / filter / collect
Rust iterators are lazy and zero-cost. Chain transformations and finally collect into a concrete container. The compiler unrolls the whole pipeline into a tight loop.
Bash
Substring + Find/Replace (parameter expansion)
Bash's ${var:offset:length} and ${var//pattern/replacement} let you do most string operations without ever spawning sed. Faster, and the syntax is portable across modern shells.
TypeScript
Promisify a Callback Function
Convert a Node-style `(err, result)` callback API into a Promise-returning function. Type-safe via generics — the inferred Promise resolves to the original callback's result type.
PHP
Build & Sign a JWT (HS256)
Generate a JWT manually using only base64-url and hash_hmac — no library required. Demonstrates header/payload/signature concatenation and the exp claim.
PHP
Business Days Between Two Dates
Count weekdays (Mon-Fri) between two dates, excluding an optional list of holidays. Direction-aware (works even if $end < $start).
PHP
cURL POST JSON
Post a JSON body with the right Content-Type header and parse the response. Returns the decoded body or throws on a non-2xx response.