a/README.md

a

a embeds a Lua interpreter and adds a standard library and IO access, so a script can reach the network, a database, the filesystem, and the terminal without additional setup.

a file.lua   # run a script
a            # start an interactive REPL

Run a with a script path to execute it, or with no arguments to start an interactive REPL.

The REPL

Running a with no arguments starts a read-eval-print loop in the same sandboxed environment used for scripts, with the full standard library available. It is convenient for trying out the library or exploring data.

• Bare expressions print their value (1 + 1 → 2); tables are pretty-printed with utils.dump.
• Statements that span several lines (a for loop, a function body) are detected as incomplete and keep reading until they parse.
• Async calls such as os.sleep, http.get, and task.join suspend and resume just as they do in a script — each entry runs on the async executor.
• Line editing and history are provided, with history persisted to ~/.a_history. Press Ctrl-D to exit (os.exit is not available in the sandbox).

Each entry is compiled as its own chunk, so a local declared on one line is not visible on the next — assign to a global (drop the local) to keep a value across entries.

What it is

a is not a Lua implementation; it embeds Lua 5.5 (via mlua) and adds the parts stock Lua omits. Plain Lua ships almost no standard library and no way to reach the outside world without C modules and a build toolchain. a provides a standard library written partly in Rust and partly in Lua, together with IO access.

The result is a single binary that runs a .lua file. There is no package manager, build step, or project scaffolding.

The standard library

The standard library is the main purpose of a. Planned surface:

• Networking — HTTP client, WebSocket, and MQTT (3.1.1 and 5).
• SQLite — access to embedded SQLite databases.
• Filesystem — read/write/glob/walk without stock Lua's io boilerplate.
• Terminal UI — interactive line editing and full-screen TUI, comparable to ncurses.

The intent is for the common case to be a single call rather than a multi-step setup.

How it works

• Embeds Lua 5.5 via mlua, on an async core (tokio) so IO-heavy scripts don't block.
• A single self-contained binary. No LuaRocks, no make, no virtualenv.
• Scripts run in a sandboxed environment modeled on Luau's safe environment: io, package, and debug are not loaded; os is trimmed to its time functions; the bytecode/chunk-loading escape hatches (load, loadfile, dofile, string.dump) are removed. The library a provides is the supported way to reach the outside world.
• A leading #! shebang line is skipped, so scripts can be made executable directly.

Building

cargo build --release
# binary at target/release/a

cargo run -- lua/test.lua   # run a script during development

Requires a Rust toolchain (2024 edition). Lua is vendored and built from source, so no system Lua is needed.