set-env-vars-via-wasi

Call a Wasm Library from Host

This example demonstrates how to set environment variables and arguments via WasmEdge wasi interface.

This example consists of two projects:

• print-env-vars is a wasm library, in which a function accessing the environment variables is defined.

• set-env-vars-via-wasi is a host application that defines a group of arguments and environment variables and sets them via WasmEdge wasi interface; then,loads the wasm binary generated from print-env-vars, and runs the wasm function exported by the wasm library to print the pre-defined arguments and environment variables.

Now let's build and run this example.

• Install rustup and Rust

  Go to the official Rust webpage and follow the instructions to install rustup and Rust.

  It is recommended to use Rust 1.71 or above in the stable channel.

  Then, add wasm32-wasi target to the Rustup toolchain:

  rustup target add wasm32-wasi

• Install WasmEdge Runtime

  Refer to the Quick Install section of WasmEdge Runtime Book to install WasmEdge Runtime. Or, use the following command directly

  # NOTICE that the installation script needs `sudo` access
  
  # install wasmedge to the directory /usr/local/
  curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | bash -s -- -v 0.14.0
  source $HOME/.wasmedge/env

  For users in China mainland (中国大陆地区), try the following command to install WasmEdge Runtime if failed to run the command above

  # NOTICE that the installation script needs `sudo` access
  
  bash install_zh.sh -v 0.14.0
  source $HOME/.wasmedge/env

• Download example

  git clone git@github.com:second-state/wasmedge-rustsdk-examples.git
  cd wasmedge-rustsdk-examples/set-env-vars-via-wasi

• Build print-env-vars

  cargo build -p print-env-vars --target wasm32-wasi --release

  If the command runs successfully, print_env_vars.wasm can be found in the directory of ./target/wasm32-wasi/release/.

• Build and run set-env-vars-via-wasi

  cargo run -p set-env-vars-via-wasi -- ./target/wasm32-wasi/release/print_env_vars.wasm

  If the command runs successfully, then the following message is printed out on the screen:

  The env vars are as follows.
  ENV1: VAL1
  ENV2: VAL2
  ENV3: VAL3
  The args are as follows.
  arg1
  arg2