node:os

A WebAssembly guest has no view of the machine it runs on. When bundled source imports node:os, Jco ensures that the selected world declares the dedicated interface, following the same in-place WIT editing described for node:child_process:

world app {
  import jco:node/os@0.1.0;
  // component imports and exports...
}

Declaring or generating the import does not grant host access: Jco’s default transpilation map uses a provider that fails every inspecting or mutating call with ERR_JCO_OS_ADAPTER_REQUIRED. Static POSIX values that reveal no machine state – EOL, devNull, and constants – resolve without a provider, so the module can be imported and used for its constants even when access is denied. An application must make the security decision explicitly, for example by mapping the Node host provider:

jco transpile component.wasm \
  --map 'jco:node/os@0.1.0=@bytecodealliance/jco-std/wasi/0.2.x/node/24.x.x/os/host/node'

That produces the call path guest node:os → WIT capability → host adapter → Node node:os.

The interface supports arch, availableParallelism, cpus, endianness, freemem, getPriority, homedir, hostname, loadavg, machine, networkInterfaces, platform, release, setPriority, tmpdir, totalmem, type, uptime, userInfo, and version, with Node’s argument validation and ERR_SYSTEM_ERROR reconstruction for failing calls.