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
Recursive Directory Walker with Predicate
Use `find -print0` + `read -d ""` to safely iterate filenames that may contain spaces, newlines, or quotes. Standard bash for-loop over `find` output breaks on these.
@admin
Kotlin
Coroutine Timeout with withTimeout
`withTimeout(ms) { ... }` cancels the inner coroutine if it doesn't finish in time and throws `TimeoutCancellationException`. `withTimeoutOrNull` returns null instead.
TypeScript
Promise with Timeout
Race a promise against a timeout — if the work takes longer than `ms`, reject with a timeout error. Cancels nothing on its own (use AbortController for that), but unblocks the caller.
PHP
Unique by Callback
Like array_unique, but the uniqueness test is a callback that returns the key to dedupe by. Useful for "unique by ID" or "unique by lowercased email" across arrays of objects/rows.
PHP
Get Nested Value by Dot Path
Read deeply-nested array values like Lodash _.get(). Use a "a.b.c" string instead of nested isset checks; returns a default on any missing segment.
SQL
EXPLAIN / EXPLAIN ANALYZE
`EXPLAIN` shows the query plan; `EXPLAIN ANALYZE` actually runs it and shows real timings. The first tool when a query is slow — look for sequential scans on big tables.
Kotlin
Coroutine Cancellation
Cancellation is cooperative — your coroutine must check via `ensureActive()`, `yield()`, or any other suspending call. CPU-busy loops without a suspend point are NOT cancellable.
SQL
DELETE with JOIN / USING
Delete rows from one table conditional on a related table. PostgreSQL uses `USING`; MySQL uses join syntax in the DELETE. Run as a SELECT first to verify what you're about to remove.
PHP
CSRF Token Generate + Verify
Per-session CSRF token helpers using hash_equals for constant-time comparison. Token is regenerated on logout but persists across requests within a session.
PHP
Validate URL (scheme + host)
Beyond filter_var, also require the URL to have an http(s) scheme and a non-empty host. Rejects "javascript:" and other risky pseudo-schemes commonly seen in stored XSS.
Bash
Array Basics (index + iterate)
Bash 4+ arrays — declare, access by index, get all elements with [@], length with #. The quoting matters: "${arr[@]}" preserves each element; ${arr[@]} word-splits.
Go
Channels — Basics
Channels are typed pipes between goroutines. Unbuffered = synchronous handoff; buffered = up to N values queued. Close a channel to signal "no more values" — receivers see ok=false.
PHP
cURL Multipart File Upload
Upload one or more files via multipart/form-data using cURL's CURLFile abstraction. No manual boundary or body construction needed.
Go
Fan-Out / Fan-In
Distribute work across N workers (fan-out), then merge their results back into one channel (fan-in). Used when you can't process items strictly in order but want to retain output as one stream.
Kotlin
Coroutine Testing with runTest
`runTest { }` from kotlinx-coroutines-test gives you a virtual time scheduler — `delay(1000)` finishes instantly while preserving ordering. No more flaky 1-second test sleeps.
Kotlin
zip and zipWithIndex
`zip` pairs elements positionally; the result is the length of the shorter list. `withIndex()` gives you `(index, value)` pairs without the manual `forEachIndexed`.
PHP
Validate IP Address (v4 + v6)
Distinguish IPv4 from IPv6, optionally reject private/reserved/loopback ranges. Useful for hardening server-side fetchers against SSRF.