node:os

Node.js os module, resolvable via both ESM import and CommonJS require. JVM-backed — every value is resolved through standard Java APIs (system properties, ManagementFactory, InetAddress) or, where the JVM has no equivalent, via FFM down-calls to POSIX symbols.

Implemented operations

Resolved at class-init (cached constants)

Operation	Source
`arch()`	`System.getProperty("os.arch")` normalised to Node's token set (`x64`, `arm64`, …)
`platform()`	Normalised `os.name` (`linux`, `darwin`, `win32`)
`type()`	`Linux` / `Darwin` / `Windows_NT`
`endianness()`	`ByteOrder.nativeOrder()` — `"LE"` / `"BE"`
`machine()`	Raw `os.arch` (e.g. `"x86_64"`, `"arm64"`)
`release()`	`os.version`
`version()`	`os.version`
`tmpdir()`	`ELIDE_SYS_TMP` environment variable if set, otherwise `java.io.tmpdir`
`homedir()`	`user.home`
`availableParallelism()`	`Runtime.availableProcessors()`
`EOL`	`"\r\n"` on Windows, `"\n"` elsewhere
`devNull`	`"\\\\.\\nul"` on Windows, `"/dev/null"` elsewhere

Dynamic

Operation	Source
`hostname()`	`InetAddress.getLocalHost().getHostName()`
`userInfo([options])`	`user.name` + `user.home` + FFM `getuid()`/`getgid()` + `SHELL` env
`networkInterfaces()`	`java.net.NetworkInterface` enumeration

`os.userInfo([options])`

Returns { username, uid, gid, shell, homedir }. Behaviour:

username — System.getProperty("user.name").
homedir — System.getProperty("user.home").
uid / gid — POSIX: FFM down-calls to the system linker's getuid / getgid. Windows (or when native access is denied): -1.
shell — POSIX: SHELL environment variable, may be null if unset. Windows: null.
options.encoding — 'buffer' returns username, homedir, and shell as UTF-8-encoded Uint8Array instances; any other value (including the default) returns them as JS strings.

javascript

const os = require("node:os");

const info = os.userInfo();
info.username; // → "alice"
info.homedir; // → "/home/alice"
info.uid; // → 1000 (POSIX), -1 (Windows)
info.shell; // → "/bin/bash" (POSIX), null (Windows)

const buf = os.userInfo({ encoding: "buffer" });
buf.username; // → Uint8Array of UTF-8 bytes

`os.networkInterfaces()`

Returns an object keyed by interface name; each value is an array of assigned address records enumerated via java.net.NetworkInterface:

address — the numeric address (IPv6 is RFC 5952-compressed, e.g. ::1).
netmask — the subnet mask.
family — the string "IPv4" or "IPv6".
mac — the hardware address as xx:xx:xx:xx:xx:xx (00:00:00:00:00:00 when the interface exposes none).
internal — true for a loopback interface.
cidr — address/prefixlen.
scopeid — the scope id (IPv6 records only).

javascript

const os = require("node:os");

const nets = os.networkInterfaces();
// → { lo: [ { address: "127.0.0.1", netmask: "255.0.0.0", family: "IPv4",
//            mac: "00:00:00:00:00:00", internal: true, cidr: "127.0.0.1/8" },
//          { address: "::1", family: "IPv6", internal: true, scopeid: 0, ... } ],
//     eth0: [ … ] }

Deferred to follow-up

These are wired into the namespace shape but throw UnsupportedOperationException on call — will be replaced by Rust-FFI paths in a later commit: cpus(), freemem(), totalmem(), uptime(), loadavg(), getPriority(), setPriority(), constants.