Arguments: argv and argc

Passing command-line arguments to your application

Cheerp supports recieving arguments in main. For example, you might have a main function that looks like this:

int main(int argc, char **argv) {
for (int i = 0; i < argc; ++i)
printf("arg: %s\n", argv[i]);
Targeting the browser
If you are targeting the browser, main is supported, but in most cases you should try to use webMain instead and recieve arguments in a different way.

The ways to provide arguments depend on which target you are compiling to.

JavaScript modules

For JavaScript modules, you can pass the arguments through the initialization function like this:

import init from "./example.js";
await init({
argv: ["a", "b", "c"],


When targeting WASI, Cheerp uses the WASI-CLI interface to get arguments, meaning that it will work on any runtime that has implemented the WASI-CLI proposal.

Terminal window
$ /opt/cheerp/bin/clang -target cheerp-wasm-wasi example.c
$ wasmtime a.out a b c


When targeting something else, you can provide environment variables and program arguments by defining a global variable called CHEERP_ARGV.

For example:

globalThis.CHEERP_ARGV = ["a", "b", "c"];


It is not possible to receive arguments in main when the main function is in a different section than the target.

Comparison to webMain

webMain cannot take arguments. To take arguments, use main.

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