Runnable Projects
Install, run, and verify real projects on your machine.
142 published
Bash CSV Column Extract
Bash CSV Column Extract — a runnable bash project with source, install and run commands, and expected output.
Bash Find Duplicate Files
Bash Find Duplicate Files — a runnable bash project with source, install and run commands, and expected output.
Bash JSON Key Extract
Bash JSON Key Extract — a runnable bash project with source, install and run commands, and expected output.
Bash Timestamp Format
Bash Timestamp Format — a runnable bash project with source, install and run commands, and expected output.
Go Base32 Codec CLI
Go Base32 Codec — a runnable go project with source, install and run commands, and expected output.
Go CSV Stats CLI
Go CSV Stats — a runnable go project with source, install and run commands, and expected output.
Go Hexdump CLI
Go Hexdump — a runnable go project with source, install and run commands, and expected output.
Go JSON Pretty-Print CLI
Go JSON Pretty-Print — a runnable go project with source, install and run commands, and expected output.
Go Levenshtein CLI
Go Levenshtein — a runnable go project with source, install and run commands, and expected output.
Go LRU Cache CLI
Go LRU Cache — a runnable go project with source, install and run commands, and expected output.
Go Priority Queue CLI
Go Priority Queue — a runnable go project with source, install and run commands, and expected output.
Go Ring Buffer CLI
Go Ring Buffer — a runnable go project with source, install and run commands, and expected output.
Go Streaming SHA-256 CLI
Go Streaming SHA-256 — a runnable go project with source, install and run commands, and expected output.
Go UUIDv7 Generator CLI
Go UUIDv7 Generator — a runnable go project with source, install and run commands, and expected output.
Java Base64 Codec CLI
Java Base64 Codec — a runnable java project with source, install and run commands, and expected output.
Java CSV Pretty-Print CLI
Java CSV Pretty-Print — a runnable java project with source, install and run commands, and expected output.
Java Priority Queue CLI
Java Priority Queue — a runnable java project with source, install and run commands, and expected output.
Java SHA-256 CLI
Java SHA-256 — a runnable java project with source, install and run commands, and expected output.
Node Minimal Argparse CLI
Node Minimal Argparse — a runnable typescript project with source, install and run commands, and expected output.
Node Binary Heap CLI
Node Binary Heap — a runnable typescript project with source, install and run commands, and expected output.
Node Bitset CLI
Node Bitset — a runnable typescript project with source, install and run commands, and expected output.
Node CSV Pretty-Print CLI
Node CSV Pretty-Print — a runnable typescript project with source, install and run commands, and expected output.
Node Debounce Batch CLI
Node Debounce Batch — a runnable typescript project with source, install and run commands, and expected output.
Node Edit Distance CLI
Node Edit Distance — a runnable typescript project with source, install and run commands, and expected output.
Node Hexdump CLI
Node Hexdump — a runnable typescript project with source, install and run commands, and expected output.
Node JSON Pointer CLI
Node JSON Pointer — a runnable typescript project with source, install and run commands, and expected output.
Node LRU Cache CLI
Node LRU Cache — a runnable typescript project with source, install and run commands, and expected output.
Node Memoized Fibonacci CLI
Node Memoized Fibonacci — a runnable typescript project with source, install and run commands, and expected output.
Node Range Merge CLI
Node Range Merge — a runnable typescript project with source, install and run commands, and expected output.
Node Regex Benchmark CLI
Node Regex Benchmark — a runnable typescript project with source, install and run commands, and expected output.
Node Ring Buffer CLI
Node Ring Buffer — a runnable typescript project with source, install and run commands, and expected output.
Node Streaming SHA-256 CLI
Node Streaming SHA-256 — a runnable typescript project with source, install and run commands, and expected output.
Node TOML to JSON CLI
Node TOML to JSON — a runnable typescript project with source, install and run commands, and expected output.
Node Topological Sort CLI
Node Topological Sort — a runnable typescript project with source, install and run commands, and expected output.
Node URL Join CLI
Node URL Join — a runnable typescript project with source, install and run commands, and expected output.
Node UUIDv7 Generator CLI
Node UUIDv7 Generator — a runnable typescript project with source, install and run commands, and expected output.
Python Argparse CLI
Python Argparse — a runnable python project with source, install and run commands, and expected output.
Python Base32 Codec CLI
Python Base32 Codec — a runnable python project with source, install and run commands, and expected output.
Python Bloom Filter CLI
Python Bloom Filter — a runnable python project with source, install and run commands, and expected output.
Python CSV Stats CLI
Python CSV Stats — a runnable python project with source, install and run commands, and expected output.
Python Memoized Fibonacci CLI
Python Memoized Fibonacci — a runnable python project with source, install and run commands, and expected output.
Python JSON Pretty-Print CLI
Python JSON Pretty-Print — a runnable python project with source, install and run commands, and expected output.
Python LRU Cache CLI
Python LRU Cache — a runnable python project with source, install and run commands, and expected output.
Python Merkle Root CLI
Python Merkle Root — a runnable python project with source, install and run commands, and expected output.
Python Priority Queue CLI
Python Priority Queue — a runnable python project with source, install and run commands, and expected output.
Python Regex Replace CLI
Python Regex Replace — a runnable python project with source, install and run commands, and expected output.
Python File SHA-256 CLI
Python File SHA-256 — a runnable python project with source, install and run commands, and expected output.
Python Topological Sort CLI
Python Topological Sort — a runnable python project with source, install and run commands, and expected output.
Rust Base64 Codec CLI
Rust Base64 Codec — a runnable rust project with source, install and run commands, and expected output.
Rust CSV Pretty-Print CLI
Rust CSV Pretty-Print — a runnable rust project with source, install and run commands, and expected output.
Rust JSON Pretty-Print CLI
Rust JSON Pretty-Print — a runnable rust project with source, install and run commands, and expected output.
Rust Levenshtein CLI
Rust Levenshtein — a runnable rust project with source, install and run commands, and expected output.
Rust LRU Cache CLI
Rust LRU Cache — a runnable rust project with source, install and run commands, and expected output.
Rust BinaryHeap CLI
Rust BinaryHeap — a runnable rust project with source, install and run commands, and expected output.
Argmax CLI
A Node CLI that reads a comma-separated number list from argv and prints the index of the maximum value, with ties going to the first.
Bloom Filter CLI
A Node CLI that builds a Bloom filter from a word list, then tests query words for probable membership with a configurable false-positive rate.
Circular Buffer CLI
A Node CLI that implements a fixed-size circular buffer, accepting push and pop commands from stdin and printing the buffer state after each operation.
Consistent Hash CLI
A Node CLI that builds a consistent hash ring from a node list and routes keys to nodes, demonstrating minimal remapping on node add or remove.
Fenwick Tree CLI
A Node CLI that builds a Fenwick tree (binary indexed tree) from an array and answers prefix-sum queries with point updates in O(log n).
HyperLogLog CLI
A Node CLI that estimates the cardinality of a stream of lines from stdin using a HyperLogLog sketch with a configurable register count.
LCS CLI
A Node CLI that computes the longest common subsequence of two strings from argv using dynamic programming and prints the LCS and its length.
LFU Cache CLI
A Node CLI that simulates an LFU (least-frequently-used) cache, processing get and put commands from stdin and printing evictions.
Markdown Strip CLI
A Node CLI that reads a Markdown file and prints the plain text with all formatting syntax removed, preserving paragraph breaks.
Priority Queue CLI
A Node CLI that implements a binary-heap priority queue, accepting push and pop commands from stdin and printing popped values in priority order.
Rolling Hash CLI
A Node CLI that computes a rolling polynomial hash over a sliding window of a file, printing the hash at each window position for block-matching.
Skip List CLI
A Node CLI that implements a skip list with probabilistic levels, accepting insert and search commands from stdin and printing search results.
Trie Autocomplete CLI
A Node CLI that builds a trie from a word list and prints autocomplete suggestions for a prefix, sorted by frequency.
Windowed Counter CLI
A Node CLI that maintains a sliding-window counter over a stream of events from stdin, printing the count in the window after each event.
Word Count CLI in Go
A Go program that counts words from a file or stdin, printing the total and the five most frequent words in descending order.
Bcrypt Hash and Verify CLI
A small Node CLI that hashes a password with bcrypt at a configurable cost and verifies a password against a stored hash.
Caesar Cipher CLI
A Node CLI that shifts letters by a configurable key for encode or decode, preserving case and non-letters, with round-trip tests.
Chmod Permission Calculator CLI
A Node CLI that converts between octal and symbolic Unix file modes, showing rwx bits and the numeric value in both directions.
CRC32 Checksum CLI
A dependency-free Node CLI that prints the CRC32 checksum of a file or stdin as an eight-digit hex string, using a precomputed lookup table.
Dotenv Validator CLI
A Node CLI that loads a .env file, checks it against a declared schema of required keys and types, and exits non-zero with a report on failure.
Duration Format CLI
A Node CLI that converts a duration in milliseconds to a compact human string such as 1h 2m 3s, and parses that format back to milliseconds.
Gzip Compress and Decompress CLI
A Node CLI that gzips stdin or a file to stdout and decompresses with gunzip, built on the streaming zlib API for bounded memory use.
HTML to Plain Text CLI
A dependency-free Node CLI that converts a small HTML document to readable plain text, honoring block breaks and decoding common entities.
HTTP Status Code Lookup CLI
A Node CLI that maps an HTTP status code to its reason phrase and category, and lists every code in a category such as 4xx.
JSON Array to CSV Converter
A Node CLI that converts an array of flat JSON objects to CSV with a stable column order and correct quoting of commas, quotes, and newlines.
JWT HS256 Sign and Verify CLI
A Node CLI that signs a JSON payload into a JWT with HS256 and verifies a token, using only the built-in crypto module and constant-time comparison.
Levenshtein Edit Distance CLI
A zero-dependency Node CLI that computes the Levenshtein edit distance between two strings, with a rolled one-row dynamic program and unit tests.
MIME Type Lookup CLI
A Node CLI that maps a file extension to its MIME type and back to common extensions, with a fallback to octet-stream.
Morse Code Encoder CLI
A Node CLI that encodes text to Morse code and decodes it back, with explicit word separators, unsupported-character reporting, and tests.
NDJSON Filter CLI
A Node CLI that reads newline-delimited JSON from stdin, keeps records matching a field selector, and writes NDJSON to stdout.
Number Format CLI with Intl
A Node CLI that formats a number for a given locale, supporting grouping, compact notation, and currency display via the Intl API.
Random Password Generator CLI
A Node CLI that generates a cryptographically random password of a chosen length using a rejection-sampled character set to avoid modulo bias.
Regex Tester CLI
A Node CLI that tests a regular expression against input text or stdin, printing every match with its index and capture groups.
Roman Numeral Converter CLI
A Node CLI that converts integers to Roman numerals and back, rejecting out-of-range and malformed input with clear errors and tests.
Semver Bump CLI
A Node CLI that bumps a semver string by major, minor, or patch according to semver rules, resetting lower components and dropping prerelease.
TOML to JSON Converter
A Node CLI that parses a minimal TOML subset (tables, key-values, strings, numbers, booleans) and prints the equivalent JSON.
UUID Validate and Inspect CLI
A Node CLI that validates a UUID string, reports its version and variant bits, and normalizes it to canonical lowercase form.
XML to JSON Converter
A Node CLI that converts a small XML document into JSON with attributes under an @ prefix and repeated children grouped into arrays.
YAML to JSON Converter in Python
A Python script that loads a YAML file with PyYAML and prints the equivalent JSON, preserving order and reporting parse errors clearly.
Simple Grep CLI in Go
A small Go program that searches a file line by line for a substring and prints matching lines with their line numbers, skipping binary files.
Zero-Dependency argv Parser
A small argv parser supporting long flags, key=value and key value pairs, and positional arguments, with strict unknown-flag detection.
Base64 Encode and Decode CLI
A small Node CLI that encodes a string to base64url or decodes a base64url string back to text, reading from an argument or stdin and printing the result.
Batch File Rename CLI with Dry Run
A Node CLI that batch-renames files in a directory using a find-and-replace pattern, defaulting to a dry run that lists planned changes before any rename happens.
Cron Next-Run Calculator
A five-field cron expression parser supporting lists, ranges, steps, and wildcards, computing the next run after a given time with minute precision.
CSV to Markdown Table Converter
A Node CLI that reads a CSV file and prints a GitHub-flavoured Markdown table, aligning columns and escaping pipe characters in cell values.
Deep JSON Diff Tool
A structural diff for two JSON documents reporting added, removed, and changed values as JSON Pointer paths, with type-change and array diffing covered.
Directory Tree Printer CLI
A Node CLI that prints a directory as an indented tree with box-drawing connectors, skipping node_modules and dotfiles and reporting total files and directories.
Env File Diff CLI
A zero-dependency CLI that parses two .env files and reports keys only on the left, only on the right, and keys whose values changed.
Dotenv File Loader
A Node module and CLI that reads a .env file, parses KEY=value lines with quoting and comments, and merges them into process.env without overwriting existing values.
Mini EventEmitter Implementation
A from-scratch event emitter with on, once, off, and emit, including listener return values and once-handler auto-removal, covered by unit tests.
FNV-1a Hash CLI with Official Vectors
A 32-bit FNV-1a hash implementation exposed as a CLI, verified against the official reference vectors for empty, short, and known input strings.
Directory Walk Statistics CLI
A streaming directory walker that reports file count, total bytes, and per-extension breakdowns, skipping symlinks by default for safe traversal.
Hex to RGB Colour Converter CLI
A Node CLI that converts a hex colour to its RGB and HSL components and converts RGB triples back to hex, validating every input format.
HTTP Fetch with Retry and Backoff
A Node module that wraps fetch with bounded retries, exponential backoff, jitter, and retryable-status detection, returning the final response or throwing.
IPv4 CIDR Calculator CLI
A Node CLI that parses an IPv4 CIDR block and prints the network address, broadcast address, netmask, and the range of usable host addresses.
Recursive JSON Secret Masker
A library and CLI that deep-masks sensitive keys in any JSON structure, handles arrays and nesting, and never touches safe keys, with tests for edge shapes.
JWT Decoder CLI
A Node CLI that decodes a JSON Web Token into its header and payload JSON without verifying the signature, and warns loudly that it does not verify.
Least-Recently-Used Cache
A Node module implementing an LRU cache with a fixed capacity, get and set with eviction, and hit and miss statistics.
Markdown TOC Generator
A CLI that extracts ATX headings from a Markdown file, builds GitHub-style anchors, and prints an indented table of contents with backtick-fenced headings handled.
Onion-Style Middleware Pipeline
A tiny Express-style middleware composer where each layer can act before and after the next, with tests proving execution order and error capture.
Pomodoro Timer CLI
A Node CLI that runs a pomodoro timer with a work interval and a break, printing a countdown and announcing each phase transition in the terminal.
Fixed-Concurrency Promise Pool
A pLimit-style concurrency limiter for async tasks with an injectable scheduler, tested to prove the pool never exceeds the limit and preserves results.
Query String Parser CLI
A Node script that parses a URL query string into an object, decoding percent-encoding, collecting repeated keys into arrays, and handling keys without values.
Sliding Window Rate Limiter
An in-memory sliding window rate limiter with an injectable clock, tested deterministically across window edges and bursts with exact verdicts.
Semantic Version Comparator CLI
A Node CLI that compares two semantic versions and reports whether the first is lower, equal, or higher, handling prerelease tags by semver precedence rules.
URL Slug Generator CLI
A Node CLI that turns a title into a URL-safe slug by lowercasing, transliterating common accented characters, and collapsing separators.
In-Memory SQLite Demo
A Node script that opens an in-memory SQLite database using the built-in node:sqlite module, creates a table, inserts rows, and queries them back.
Old Temp File Cleanup CLI
A Node CLI that scans a temporary directory, finds files older than a given age, reports reclaimable space, and deletes them only when a confirm flag is passed.
Character Frequency Histogram CLI
A standard-library CLI that counts letter and digit frequencies in a text file and prints a sorted ASCII bar chart for the top characters.
Text Wrapping CLI
A Node CLI that wraps a paragraph to a target width without breaking words, and optionally indents each wrapped line for quote or code formatting.
TOTP Generator with RFC 6238 Vectors
A dependency-free TOTP implementation using HMAC-SHA1 through the crypto module, verified against the official RFC 6238 appendix test vectors.
UUID v4 Generator CLI
A minimal CLI that prints cryptographically random RFC 4122 version 4 UUIDs using the built-in crypto module, one per line, with format validation.
Minimal YAML to JSON Converter
A Node script that parses a small, common subset of YAML (key-value pairs, nested maps, and simple lists) and prints the equivalent JSON document.
Directory Size Report in Python
A Python script that walks a directory, sums file sizes per immediate subdirectory, and prints a descending report with absolute and relative sizes.
INI to JSON Converter in Python
A Python script that reads an INI configuration file with configparser and prints it as nested JSON, converting numeric and boolean values.
JSON Lines Statistics Script
A Python script that reads a JSON Lines file, counts records, reports the keys present, and computes basic statistics for numeric fields.
File Checksum Verifier in Python
A Python script that computes a SHA-256 checksum for each file in a directory and compares them against a checksums file to report mismatches.
SQLite Todo CLI in Python
A Python CLI that stores todos in a SQLite database with add, list, and done commands, using the standard library sqlite3 module only.
Word Frequency Counter in Python
A Python script that reads a text file, counts word frequencies with a stop-word filter, and prints the most common words with their counts.
Bash Log Rotation Script
A small Bash script that finds .log files older than a threshold, supports a dry run, and compresses matched files with gzip.
Node.js JSON API with the Standard Library
A dependency-free HTTP API with health, list, and 404 endpoints, plus an automated test that starts the server on an ephemeral port and verifies each response.
Node.js Static File Server with Traversal Protection
A dependency-free static file server with content-type detection, 404 handling, and a path-traversal guard, verified by a test that serves a temporary directory.
Word Count CLI in Node.js
A small command-line tool that reports lines, words, and UTF-8 bytes for a file, with unit and CLI tests that verify output and error handling.
CSV to JSON Converter in Python
A standard-library CLI that converts a CSV file with headers into a JSON array and reports the number of rows converted.
Python Health Check Server
A standard-library HTTP server with health and JSON 404 endpoints, plus unittest coverage that starts the server on an ephemeral port.
FastAPI Hello API — Runnable Python Project
A minimal FastAPI project with a health endpoint, a greeting endpoint with path/query parameters, and auto-generated OpenAPI docs. Includes source, dependencies, and test suite.
Markdown to HTML CLI — Runnable TypeScript Project
A TypeScript CLI tool that converts Markdown to styled HTML. Includes source code, npm scripts, and test suite for immediate execution.
Task Tracker CLI — Runnable Deno Project
A Deno task tracker CLI that stores todos in a local JSON file. Includes full source code, build instructions, and test suite to validate core operations.