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
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.
@admin
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.
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 `&`.
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).
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.
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.
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.
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.
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.
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.
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."
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.
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.
Kotlin
Room — Android Database
Room is the official Android persistence library — annotation-driven, compile-time SQL verification, coroutine + Flow integration out of the box.
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.
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.
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.