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smart-city-digital-twin-mar…/smart-app-city/frontend/node_modules/@expo/spawn-async/README.md
Eric FELIXINE e30ae8ed09 feat(smart-app): implement complete mobile app MVP
- App.tsx: full navigation (Auth stack + Main tabs with 5 screens)
- Auth: LoginScreen, RegisterScreen, ForgotPasswordScreen
- HomeScreen: dashboard with IoT metrics, weather widget, alerts, quick actions, sensors
- MapScreen: interactive map with layer toggles (6 layers)
- MarketplaceScreen: categories (6), products (5), search
- ChatScreen: AI chat with quick prompts (4), bot responses
- ProfileScreen: user info, stats, menu (9 items), logout
- AlertsScreen: alert list with severity, acknowledge
- SensorsScreen: sensor list with type filters (6 types), search
- ZonesScreen: zone cards with stats
- SettingsScreen: language picker (FR/EN/ES/DE), privacy, about
- Stores: iotStore (sensors, zones, alerts), notificationStore, uiStore + i18n
- Hooks: useSensors, useAlerts, useNotifications, useLocation
- Components: Card, Button, LoadingSpinner, ErrorBoundary, Header
- Services: iotService, notificationService (with axios API client)
- Utils: formatters (temp, AQI, noise, dates), validators (email, password, IBAN)
- Theme: colors.ts with full design system (Blue Ocean palette)
- Ditto: fixed MongoDB connection, new JWT secrets, official gateway image
2026-06-01 18:00:35 -04:00

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# spawn-async [![Tests](https://github.com/expo/spawn-async/actions/workflows/main.yml/badge.svg)](https://github.com/expo/spawn-async/actions/workflows/main.yml)
A cross-platform version of Node's `child_process.spawn` as an async function that returns a promise. Supports Node 12 LTS and up.
## Usage:
```js
import spawnAsync from '@expo/spawn-async';
(async function () {
let resultPromise = spawnAsync('echo', ['hello', 'world']);
let spawnedChildProcess = resultPromise.child;
try {
let {
pid,
output: [stdout, stderr],
stdout,
stderr,
status,
signal,
} = await resultPromise;
} catch (e) {
console.error(e.stack);
// The error object also has the same properties as the result object
}
})();
```
## API
`spawnAsync` takes the same arguments as [`child_process.spawn`](https://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options). Its options are the same as those of `child_process.spawn` plus:
- `ignoreStdio`: whether to ignore waiting for the child process's stdio streams to close before resolving the result promise. When ignoring stdio, the returned values for `stdout` and `stderr` will be empty strings. The default value of this option is `false`.
- `maxBuffer`: the maximum bytes retained from `stdout` and `stderr` (independently). Output is collected with a sliding window. When set explicitly, exceeding it rejects the promise with an error whose `code` is `ERR_CHILD_PROCESS_STDIO_MAXBUFFER` and whose `stdout`/`stderr` carry the truncated tail. When omitted, the default is `buffer.constants.MAX_STRING_LENGTH` (~512 MiB).
It returns a promise whose result is an object with these properties:
- `pid`: the process ID of the spawned child process
- `output`: an array with stdout and stderr's output
- `stdout`: a string of what the child process wrote to stdout
- `stderr`: a string of what the child process wrote to stderr
- `status`: the exit code of the child process
- `signal`: the signal (ex: `SIGTERM`) used to stop the child process if it did not exit on its own
If there's an error running the child process or it exits with a non-zero status code, `spawnAsync` rejects the returned promise. The Error object also has the properties listed above.
### Accessing the child process
Sometimes you may want to access the child process object--for example, if you wanted to attach event handlers to `stdio` or `stderr` and process data as it is available instead of waiting for the process to be resolved.
You can do this by accessing `.child` on the Promise that is returned by `spawnAsync`.
Here is an example:
```js
(async () => {
let ffmpeg$ = spawnAsync('ffmpeg', ['-i', 'path/to/source.flac', '-codec:a', 'libmp3lame', '-b:a', '320k', '-ar', '44100', 'path/to/output.mp3']);
let childProcess = ffmpeg$.child;
childProcess.stdout.on('data', (data) => {
console.log(`ffmpeg stdout: ${data}`);
});
childProcess.stderr.on('data', (data) => {
console.error(`ffmpeg stderr: ${data}`);
});
let result = await ffmpeg$;
console.log(`ffmpeg pid ${result.pid} exited with code ${result.code}`);
})();
```
## Notes
### `maxBuffer`
`maxBuffer` is a later addition to the API. Set it when child output could exhaust memory and crash the parent process, or when the command or arguments are influenced by untrusted input — an attacker can otherwise force unbounded output to crash the parent.
The default of `buffer.constants.MAX_STRING_LENGTH` (~512 MiB) is a crash-safe floor, not a memory bound: at that size the materialized string itself can still exhaust process memory.
When `maxBuffer` is set explicitly, exceeding it rejects the promise immediately with `ERR_CHILD_PROCESS_STDIO_MAXBUFFER`. When left at the default, exceeding it doesn't reject; the sliding-window tail is still readable, but reading `stdout`/`stderr` throws `ERR_CHILD_PROCESS_STDIO_MAXBUFFER` with the truncated tail attached.