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A toy Rust application compiled to WASI WebAssembly
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Rust WASI Example

A toy program implementing HQ9+ to demo compiling Rust to WASI and running it with Wasmer.

Setting up

First, let's clone the repo:

git clone
cd rust-wasi-example

Ensure you have an up to date version of Rust nightly and run:

rustup target add wasm32-wasi --toolchain nightly


cargo +nightly build --target=wasm32-wasi --release
cp target/wasm32-unknown-wasi/release/wasi-example.wasm .


# Install wasmer
curl -sSfL | sh

# Run the WebAssembly file with Wasmer!
wasmer run wasi-example.wasm -- -e "HQ9+"

# Run again, giving access to the current directory and passing a file to `hq9+`
wasmer run wasi-example.wasm --dir=. -- -f examples/test.hq9+

Uploading to WAPM

Setting up wapm cli

To upload to WAPM we must first make an account:

  1. Go to
  2. Create an account (sign up)
  3. Log in with the wapm cli client
# Log in to WAPM
wapm login
# Enter username and password

# Success!

Setting up the project for wapm

To run the project with wapm we must create a wapm.toml manifest file to instruct wapm how to run the wasm binary.

Our wapm.toml contains 3 sections:

  • [package] This is where the metadata about the package lives
  • [[module]] This is where metadata about the module (wasm binary) lives
  • [[command]] This is where we tell wapm how to run the module and what to call it

For more information about these sections see the documentation.

IMPORTANT: To publish the project to the wapm registry, you must change the namespace (the field before the /) to match the username you made while signing up and that you are now logged in as (wapm whoami).

For your convenience, you may run the following snippet to edit it for you.

# Update the example `wapm.toml` to be namespaced under your name
sed -i '' "s/YOUR-USERNAME/$(wapm whoami)/" wapm.toml

When making a new wapm project, this step is not necessary; the wapm init command creates a wapm.toml skeleton, with your name as the namespace, for you.

Running the project with wapm locally

Now that we're all set up, we can use wapm to run our wasm binary!

# Run our module using `--` as a divider to avoid the ambiguity of who should process the argument
wapm run hq9+ -- --help

# Run our module without a divider as a convenience, `-e`valuating some HQ9+ source code
wapm run hq9+ -e "+9QH"

Uploading to WAPM

Now that we've set up wapm and verified that it works locally, we're ready to upload to the WAPM registry:

# Upload to the wapm registry!
wapm publish

# Success!

Running from WAPM

# Make a clean directory to test installing and running our wapm module
mkdir ../wapm-test
cd ../wapm-test

# Install from the registry, this will create a lockfile for us
wapm install YOUR-USERNAME/rust-example

# Run the command we made in our package
wapm run hq9+ -e "H"

# Run a source file, by pre-opening the current directory and passing the source file as an argument to hq9+
wapm run hq9+ --dir=. -f examples/test.hq9+
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