in-container

Detect whether the current process is running inside a container (Docker or Podman) — inDocker()/inPodman() check filesystem/cgroup signals, inContainer() is their OR. Zero dependencies, async/sync flavors, resolves false (never throws; heuristic, forgeable) with no signal, e.g. Windows/macOS hosts or other runtimes.

Node.js >=14.18.0; CLI needs >=16.17.0 <17.0.0 or >=18.3.0 for parseArgs. ESM and CommonJS.

npm install in-container

Usage

import { inContainer } from 'in-container/async'; // or 'in-container/sync'

if (await inContainer()) console.log('Running inside a container');

The root re-exports inDocker/inPodman/inContainer under async()/ sync() namespace functions, a default export grouping them (container by convention), and flat Async/Sync-suffixed functions — the two forms require opposite call styles:

• Namespace functions (container.async(), etc.) must be called attached to container — they return an object whose own methods must, in turn, stay attached to that returned object.
• Flat functions (inContainerAsync, etc.) must be destructured — call them standalone, not dotted off container.

import container, { inContainerAsync } from 'in-container';

await container.async().inDocker(); // ok: async() called attached to container
await inContainerAsync(); // ok: destructured out

const { async } = container;
async(); // throws: async pulled off container, called detached

const { inDocker } = container.async();
inDocker(); // throws: pulled out of the returned namespace

container.inContainerAsync(); // throws: called attached, not destructured

async/sync also aren't importable as named exports — only reachable via the default export.

CommonJS has no default/named split — require() returns that same object, so the same rules apply straight off it:

const container = require('in-container');
const { inContainerSync } = container;

container.sync().inDocker(); // ok
inContainerSync(); // ok

CLI

npx in-container [-q|--quiet] [-h|--help] [-v|--version]

Prints {"container":true,"docker":true,"podman":false}, exits 0/1/2 for detected/not detected/invalid usage; --quiet skips the JSON.

Development

pnpm install && pnpm build   # dist/ + type declarations
pnpm format                  # prettier

MIT licensed.