wasmz implements WASI Preview 1 (snapshot 1), enabling WebAssembly modules to interact with the host system.
All WASI Preview 1 functions are implemented:
Function Status
args_get✅ args_sizes_get✅ environ_get✅ environ_sizes_get✅
Function Status
clock_res_get✅ clock_time_get✅
Function Status
fd_advise✅ fd_allocate✅ fd_close✅ fd_datasync✅ fd_fdstat_get✅ fd_fdstat_set_flags✅ fd_fdstat_set_rights✅ fd_filestat_get✅ fd_filestat_set_size✅ fd_filestat_set_times✅ fd_pread✅ fd_prestat_get✅ fd_prestat_dir_name✅ fd_pwrite✅ fd_read✅ fd_readdir✅ fd_renumber✅ fd_seek✅ fd_sync✅ fd_tell✅ fd_write✅
Function Status
path_create_directory✅ path_filestat_get✅ path_filestat_set_times✅ path_link✅ path_open✅ path_readlink✅ path_remove_directory✅ path_rename✅ path_symlink✅ path_unlink_file✅
Function Status
poll_oneoff✅
Function Status
proc_exit✅ proc_raise✅ sched_yield✅
Function Status
random_get✅
Function Status
sock_accept✅ sock_recv✅ sock_send✅ sock_shutdown✅
# Pass arguments to WASM module
wasmz program.wasm --args "arg1 arg2 'arg with spaces'"
Environment variables are automatically inherited from the host process.
const wasi = @import("wasi").preview1;
// Create WASI host
var wasi_host = wasi.Host.init(allocator);
defer wasi_host.deinit();
// Set arguments
try wasi_host.setArgs(&[_][]const u8{
"program.wasm",
"--verbose",
"input.txt",
});
// Set environment variables
try wasi_host.setEnv("MY_VAR", "value");
// Pre-open directory
try wasi_host.preopenDir("/data", "/data");
// Add to linker
var linker = wasmz.Linker.empty;
try wasi_host.addToLinker(&linker, allocator);
WASI uses pre-opened directories for filesystem access. By default:
/ is pre-opened as the current working directoryAdditional directories can be pre-opened via the API
// Pre-open specific directories
try wasi_host.preopenDir("/tmp", "/tmp");
try wasi_host.preopenDir("/home/user/data", "/data");
When a WASM module calls proc_exit, the exit code is returned:
const result = try instance.call("_start", &.{});
if (result.trap) |trap| {
if (trap.code == .Exit) {
const exit_code = trap.exit_code;
// Handle exit code
}
}
Register a callback for proc_exit:
fn onExit(code: u32, ctx: ?*anyopaque) void {
std.debug.print("Module exited with code {d}\n", .{code});
}
wasi_host.setOnExit(onExit, &my_context);
WASI Preview 2 (Component Model) is not yet supported .