Interacting with the Filesystem using WASI in Go

WebAssembly (Wasm) and WebAssembly System Interface (WASI) are powerful technologies that allow you to run code written in various programming languages in a sandboxed environment. In this blog post, we’ll create a simple Go program that interacts with the filesystem using WASI. We’ll also set up the environment using Nix to ensure reproducibility.

Prerequisites

1. Install Nix: Nix is a powerful package manager that ensures reproducible builds. You can install it by following the instructions on the Nix website.

Step 1: Set Up the Environment

First, let’s create a directory for our project and set up a Nix shell to ensure we have the necessary tools installed.

mkdir wasm-ws
cd wasm-ws
touch run.sh

Create a run.sh script to set up the Nix environment:

cat <<EOF > run.sh
#!/bin/sh
nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz -p tinygo wasmtime -v
EOF

Make the script executable:

chmod +x run.sh

Now, run the script to enter the Nix shell:

./run.sh

Step 2: Write the Go Code

Create a file named main.go with the following content:

package main

import (
    "fmt"
    "io/ioutil"
    "os"
)

func main() {
    // Open the file…