Welcome to WASI!
WASI stands for WebAssembly System Interface. It's an API designed by the Wasmtime project that provides access to several operating-system-like features, including files and filesystems, Berkeley sockets, clocks, and random numbers, that we'll be proposing for standardization.
It's designed to be independent of browsers, so it doesn't depend on Web APIs or JS, and isn't limited by the need to be compatible with JS. And it has integrated capability-based security, so it extends WebAssembly's characteristic sandboxing to include I/O.
Note that everything here is a prototype, and while a lot of stuff works, there are numerous missing features and some rough edges. For example, networking support is incomplete.
How can I write programs that use WASI?
The two toolchains that currently work well are the Rust toolchain and a specially packaged C and C++ toolchain. Of course, we hope other toolchains will be able to implement WASI as well!
To install a WASI-enabled Rust toolchain, see the online section of the guide
To install a WASI-enabled C/C++ toolchain, see the online section of the guide
How can I run programs that use WASI?
Wasmtime is a non-Web WebAssembly engine which is part of the
Bytecode Alliance project. To build
it, download the code and build with
cargo build --release. It can
run WASI-using wasm programs by simply running
cargo run --bin wasmtime foo.wasm.
The browser polyfill
The polyfill is online here.
The source is here.