bellpull
API reference

bellpull/cross-spawn

Every export of bellpull/cross-spawn, with its signature and doc comment: _enoent, crossSpawn, module.exports, parse, spawn, sync and 2 more, plus 3 types.

bellpull/cross-spawn — the drop-in path for cross-spawn (design R7, Y3).

Graded by cross-spawn's own 68-case suite in compat-oracle (hosts.ts, target: 'bellpull/cross-spawn'). The suite runs every case four times — spawn, spawn-force-shell, sync, sync-force-shell — so a divergence in one path cannot hide behind the other three.

What a drop-in means here, and the one thing it means most

On POSIX this is a pass-through, and that is the correct implementation. cross-spawn's own parseNonShell returns immediately off Windows; its hookChildProcess does too. Everything it is famous for — npm.cmd, PATHEXT, shebangs, caret escaping — is Windows-only, because on POSIX the kernel already does all of it. A façade that "improved" on that by resolving the command itself would change the error a caller sees (err.path would be a resolved path, not the name they wrote), change the process tree, and break the incumbent's suite in four places. Being identical is the product.

So what this file adds over node:child_process is exactly what cross-spawn adds: argument normalisation and cloning, the Windows parse in spawn-args.ts, and the ENOENT reconstruction in enoent.ts.

It reads the ambient process, on purpose

The core (run.ts, which.ts) takes a Runtime argument and reads no global — Y9. A drop-in cannot: cross-spawn's callers pass a command and some arguments, and the package reads process.env and process.platform itself. Requiring a runtime here would mean every migrating caller edits every call site, which is the definition of not a drop-in. ambient.ts is where that read lives, once.

Default export

module.exports = spawn with spawn, sync, _parse and _enoent hung off it, because that is what require('cross-spawn') gives today and a migration must not have to change how the value is called.

import crossSpawn from 'bellpull/cross-spawn';
import { _enoent, crossSpawn, module.exports, … } from 'bellpull/cross-spawn';

Functions

parse

cross-spawn._parse: exported because its suite and its ecosystem both reach for it.

function parse(command: string, args?: ArgsOrOptions, options?: SpawnOptions | null): Parsed;
ParameterType
commandstring
args (optional)ArgsOrOptions
options (optional)SpawnOptions | null

Returns Parsed

spawn

cross-spawn(command, args?, options?) — a ChildProcess, spawned the way the platform needs.

function spawn(command: string, args?: ArgsOrOptions, options?: SpawnOptions | null): ChildProcess;
ParameterType
commandstring
args (optional)ArgsOrOptions
options (optional)SpawnOptions | null

Returns ChildProcess

sync

cross-spawn.sync(command, args?, options?).

The missing-command case is put back onto result.error rather than thrown: spawnSync reports a failure to start that way and a drop-in that threw would turn a value the caller inspects into control flow they did not write.

function sync(command: string, args?: ArgsOrOptions, options?: SpawnOptions | null): SpawnSyncReturns<Buffer | string>;
ParameterType
commandstring
args (optional)ArgsOrOptions
options (optional)SpawnOptions | null

Returns SpawnSyncReturns<Buffer \| string>

Classes

ChildProcess

Instances of the ChildProcess represent spawned child processes.

Instances of ChildProcess are not intended to be created directly. Rather, use the {@link spawn}, {@link exec},{@link execFile}, or {@link fork} methods to create instances of ChildProcess.

class ChildProcess implements EventEmitter {
        /**
         * A `Writable Stream` that represents the child process's `stdin`.
         *
         * If a child process waits to read all of its input, the child will not continue
         * until this stream has been closed via `end()`.
         *
         * If the child was spawned with `stdio[0]` set to anything other than `'pipe'`,
         * then this will be `null`.
         *
         * `subprocess.stdin` is an alias for `subprocess.stdio[0]`. Both properties will
         * refer to the same value.
         *
         * The `subprocess.stdin` property can be `null` or `undefined` if the child process could not be successfully spawned.
         * @since v0.1.90
         */
        stdin: Writable | null;
        /**
         * A `Readable Stream` that represents the child process's `stdout`.
         *
         * If the child was spawned with `stdio[1]` set to anything other than `'pipe'`,
         * then this will be `null`.
         *
         * `subprocess.stdout` is an alias for `subprocess.stdio[1]`. Both properties will
         * refer to the same value.
         *
         * ```js
         * import { spawn } from 'node:child_process';
         *
         * const subprocess = spawn('ls');
         *
         * subprocess.stdout.on('data', (data) => {
         *   console.log(`Received chunk ${data}`);
         * });
         * ```
         *
         * The `subprocess.stdout` property can be `null` or `undefined` if the child process could not be successfully spawned.
         * @since v0.1.90
         */
        stdout: Readable | null;
        /**
         * A `Readable Stream` that represents the child process's `stderr`.
         *
         * If the child was spawned with `stdio[2]` set to anything other than `'pipe'`,
         * then this will be `null`.
         *
         * `subprocess.stderr` is an alias for `subprocess.stdio[2]`. Both properties will
         * refer to the same value.
         *
         * The `subprocess.stderr` property can be `null` or `undefined` if the child process could not be successfully spawned.
         * @since v0.1.90
         */
        stderr: Readable | null;
        /**
         * The `subprocess.channel` property is a reference to the child's IPC channel. If
         * no IPC channel exists, this property is `undefined`.
         * @since v7.1.0
         */
        readonly channel?: Control | null;
        /**
         * A sparse array of pipes to the child process, corresponding with positions in
         * the `stdio` option passed to {@link spawn} that have been set
         * to the value `'pipe'`. `subprocess.stdio[0]`, `subprocess.stdio[1]`, and `subprocess.stdio[2]` are also available as `subprocess.stdin`, `subprocess.stdout`, and `subprocess.stderr`,
         * respectively.
         *
         * In the following example, only the child's fd `1` (stdout) is configured as a
         * pipe, so only the parent's `subprocess.stdio[1]` is a stream, all other values
         * in the array are `null`.
         *
         * ```js
         * import assert from 'node:assert';
         * import fs from 'node:fs';
         * import child_process from 'node:child_process';
         *
         * const subprocess = child_process.spawn('ls', {
         *   stdio: [
         *     0, // Use parent's stdin for child.
         *     'pipe', // Pipe child's stdout to parent.
         *     fs.openSync('err.out', 'w'), // Direct child's stderr to a file.
         *   ],
         * });
         *
         * assert.strictEqual(subprocess.stdio[0], null);
         * assert.strictEqual(subprocess.stdio[0], subprocess.stdin);
         *
         * assert(subprocess.stdout);
         * assert.strictEqual(subprocess.stdio[1], subprocess.stdout);
         *
         * assert.strictEqual(subprocess.stdio[2], null);
         * assert.strictEqual(subprocess.stdio[2], subprocess.stderr);
         * ```
         *
         * The `subprocess.stdio` property can be `undefined` if the child process could
         * not be successfully spawned.
         * @since v0.7.10
         */
        readonly stdio: [
            Writable | null,
            // stdin
            Readable | null,
            // stdout
            Readable | null,
            // stderr
            Readable | Writable | null | undefined,
            // extra
            Readable | Writable | null | undefined, // extra
        ];
        /**
         * The `subprocess.killed` property indicates whether the child process
         * successfully received a signal from `subprocess.kill()`. The `killed` property
         * does not indicate that the child process has been terminated.
         * @since v0.5.10
         */
        readonly killed: boolean;
        /**
         * Returns the process identifier (PID) of the child process. If the child process
         * fails to spawn due to errors, then the value is `undefined` and `error` is
         * emitted.
         *
         * ```js
         * import { spawn } from 'node:child_process';
         * const grep = spawn('grep', ['ssh']);
         *
         * console.log(`Spawned child pid: ${grep.pid}`);
         * grep.stdin.end();
         * ```
         * @since v0.1.90
         */
        readonly pid?: number | undefined;
        /**
         * The `subprocess.connected` property indicates whether it is still possible to
         * send and receive messages from a child process. When `subprocess.connected` is `false`, it is no longer possible to send or receive messages.
         * @since v0.7.2
         */
        readonly connected: boolean;
        /**
         * The `subprocess.exitCode` property indicates the exit code of the child process.
         * If the child process is still running, the field will be `null`.
         *
         * When the child process is terminated by a signal, `subprocess.exitCode` will be
         * `null` and `subprocess.signalCode` will be set. To get the corresponding
         * POSIX exit code, use
         * `util.convertProcessSignalToExitCode(subprocess.signalCode)`.
         */
        readonly exitCode: number | null;
        /**
         * The `subprocess.signalCode` property indicates the signal received by
         * the child process if any, else `null`.
         */
        readonly signalCode: NodeJS.Signals | null;
        /**
         * The `subprocess.spawnargs` property represents the full list of command-line
         * arguments the child process was launched with.
         */
        readonly spawnargs: string[];
        /**
         * The `subprocess.spawnfile` property indicates the executable file name of
         * the child process that is launched.
         *
         * For {@link fork}, its value will be equal to `process.execPath`.
         * For {@link spawn}, its value will be the name of
         * the executable file.
         * For {@link exec},  its value will be the name of the shell
         * in which the child process is launched.
         */
        readonly spawnfile: string;
        /**
         * The `subprocess.kill()` method sends a signal to the child process. If no
         * argument is given, the process will be sent the `'SIGTERM'` signal. See [`signal(7)`](http://man7.org/linux/man-pages/man7/signal.7.html) for a list of available signals. This function
         * returns `true` if [`kill(2)`](http://man7.org/linux/man-pages/man2/kill.2.html) succeeds, and `false` otherwise.
         *
         * ```js
         * import { spawn } from 'node:child_process';
         * const grep = spawn('grep', ['ssh']);
         *
         * grep.on('close', (code, signal) => {
         *   console.log(
         *     `child process terminated due to receipt of signal ${signal}`);
         * });
         *
         * // Send SIGHUP to process.
         * grep.kill('SIGHUP');
         * ```
         *
         * The `ChildProcess` object may emit an `'error'` event if the signal
         * cannot be delivered. Sending a signal to a child process that has already exited
         * is not an error but may have unforeseen consequences. Specifically, if the
         * process identifier (PID) has been reassigned to another process, the signal will
         * be delivered to that process instead which can have unexpected results.
         *
         * While the function is called `kill`, the signal delivered to the child process
         * may not actually terminate the process.
         *
         * See [`kill(2)`](http://man7.org/linux/man-pages/man2/kill.2.html) for reference.
         *
         * On Windows, where POSIX signals do not exist, the `signal` argument will be
         * ignored, and the process will be killed forcefully and abruptly (similar to `'SIGKILL'`).
         * See `Signal Events` for more details.
         *
         * On Linux, child processes of child processes will not be terminated
         * when attempting to kill their parent. This is likely to happen when running a
         * new process in a shell or with the use of the `shell` option of `ChildProcess`:
         *
         * ```js
         * import { spawn } from 'node:child_process';
         *
         * const subprocess = spawn(
         *   'sh',
         *   [
         *     '-c',
         *     `node -e "setInterval(() => {
         *       console.log(process.pid, 'is alive')
         *     }, 500);"`,
         *   ], {
         *     stdio: ['inherit', 'inherit', 'inherit'],
         *   },
         * );
         *
         * setTimeout(() => {
         *   subprocess.kill(); // Does not terminate the Node.js process in the shell.
         * }, 2000);
         * ```
         * @since v0.1.90
         */
        kill(signal?: NodeJS.Signals | number): boolean;
        /**
         * Calls {@link ChildProcess.kill} with `'SIGTERM'`.
         * @since v20.5.0
         */
        [Symbol.dispose](): void;
        /**
         * When an IPC channel has been established between the parent and child (
         * i.e. when using {@link fork}), the `subprocess.send()` method can
         * be used to send messages to the child process. When the child process is a
         * Node.js instance, these messages can be received via the `'message'` event.
         *
         * The message goes through serialization and parsing. The resulting
         * message might not be the same as what is originally sent.
         *
         * For example, in the parent script:
         *
         * ```js
         * import cp from 'node:child_process';
         * const n = cp.fork(`${__dirname}/sub.js`);
         *
         * n.on('message', (m) => {
         *   console.log('PARENT got message:', m);
         * });
         *
         * // Causes the child to print: CHILD got message: { hello: 'world' }
         * n.send({ hello: 'world' });
         * ```
         *
         * And then the child script, `'sub.js'` might look like this:
         *
         * ```js
         * process.on('message', (m) => {
         *   console.log('CHILD got message:', m);
         * });
         *
         * // Causes the parent to print: PARENT got message: { foo: 'bar', baz: null }
         * process.send({ foo: 'bar', baz: NaN });
         * ```
         *
         * Child Node.js processes will have a `process.send()` method of their own
         * that allows the child to send messages back to the parent.
         *
         * There is a special case when sending a `{cmd: 'NODE_foo'}` message. Messages
         * containing a `NODE_` prefix in the `cmd` property are reserved for use within
         * Node.js core and will not be emitted in the child's `'message'` event. Rather, such messages are emitted using the `'internalMessage'` event and are consumed internally by Node.js.
         * Applications should avoid using such messages or listening for `'internalMessage'` events as it is subject to change without notice.
         *
         * The optional `sendHandle` argument that may be passed to `subprocess.send()` is
         * for passing a TCP server or socket object to the child process. The child will
         * receive the object as the second argument passed to the callback function
         * registered on the `'message'` event. Any data that is received and buffered in
         * the socket will not be sent to the child. Sending IPC sockets is not supported on Windows.
         *
         * The optional `callback` is a function that is invoked after the message is
         * sent but before the child may have received it. The function is called with a
         * single argument: `null` on success, or an `Error` object on failure.
         *
         * If no `callback` function is provided and the message cannot be sent, an `'error'` event will be emitted by the `ChildProcess` object. This can
         * happen, for instance, when the child process has already exited.
         *
         * `subprocess.send()` will return `false` if the channel has closed or when the
         * backlog of unsent messages exceeds a threshold that makes it unwise to send
         * more. Otherwise, the method returns `true`. The `callback` function can be
         * used to implement flow control.
         *
         * #### Example: sending a server object
         *
         * The `sendHandle` argument can be used, for instance, to pass the handle of
         * a TCP server object to the child process as illustrated in the example below:
         *
         * ```js
         * import { createServer } from 'node:net';
         * import { fork } from 'node:child_process';
         * const subprocess = fork('subprocess.js');
         *
         * // Open up the server object and send the handle.
         * const server = createServer();
         * server.on('connection', (socket) => {
         *   socket.end('handled by parent');
         * });
         * server.listen(1337, () => {
         *   subprocess.send('server', server);
         * });
         * ```
         *
         * The child would then receive the server object as:
         *
         * ```js
         * process.on('message', (m, server) => {
         *   if (m === 'server') {
         *     server.on('connection', (socket) => {
         *       socket.end('handled by child');
         *     });
         *   }
         * });
         * ```
         *
         * Once the server is now shared between the parent and child, some connections
         * can be handled by the parent and some by the child.
         *
         * While the example above uses a server created using the `node:net` module, `node:dgram` module servers use exactly the same workflow with the exceptions of
         * listening on a `'message'` event instead of `'connection'` and using `server.bind()` instead of `server.listen()`. This is, however, only
         * supported on Unix platforms.
         *
         * #### Example: sending a socket object
         *
         * Similarly, the `sendHandler` argument can be used to pass the handle of a
         * socket to the child process. The example below spawns two children that each
         * handle connections with "normal" or "special" priority:
         *
         * ```js
         * import { createServer } from 'node:net';
         * import { fork } from 'node:child_process';
         * const normal = fork('subprocess.js', ['normal']);
         * const special = fork('subprocess.js', ['special']);
         *
         * // Open up the server and send sockets to child. Use pauseOnConnect to prevent
         * // the sockets from being read before they are sent to the child process.
         * const server = createServer({ pauseOnConnect: true });
         * server.on('connection', (socket) => {
         *
         *   // If this is special priority...
         *   if (socket.remoteAddress === '74.125.127.100') {
         *     special.send('socket', socket);
         *     return;
         *   }
         *   // This is normal priority.
         *   normal.send('socket', socket);
         * });
         * server.listen(1337);
         * ```
         *
         * The `subprocess.js` would receive the socket handle as the second argument
         * passed to the event callback function:
         *
         * ```js
         * process.on('message', (m, socket) => {
         *   if (m === 'socket') {
         *     if (socket) {
         *       // Check that the client socket exists.
         *       // It is possible for the socket to be closed between the time it is
         *       // sent and the time it is received in the child process.
         *       socket.end(`Request handled with ${process.argv[2]} priority`);
         *     }
         *   }
         * });
         * ```
         *
         * Do not use `.maxConnections` on a socket that has been passed to a subprocess.
         * The parent cannot track when the socket is destroyed.
         *
         * Any `'message'` handlers in the subprocess should verify that `socket` exists,
         * as the connection may have been closed during the time it takes to send the
         * connection to the child.
         * @since v0.5.9
         * @param sendHandle `undefined`, or a [`net.Socket`](https://nodejs.org/docs/latest-v26.x/api/net.html#class-netsocket), [`net.Server`](https://nodejs.org/docs/latest-v26.x/api/net.html#class-netserver), or [`dgram.Socket`](https://nodejs.org/docs/latest-v26.x/api/dgram.html#class-dgramsocket) object.
         * @param options The `options` argument, if present, is an object used to parameterize the sending of certain types of handles. `options` supports the following properties:
         */
        send(message: Serializable, callback?: (error: Error | null) => void): boolean;
        send(message: Serializable, sendHandle?: SendHandle, callback?: (error: Error | null) => void): boolean;
        send(
            message: Serializable,
            sendHandle?: SendHandle,
            options?: MessageOptions,
            callback?: (error: Error | null) => void,
        ): boolean;
        /**
         * Closes the IPC channel between parent and child, allowing the child to exit
         * gracefully once there are no other connections keeping it alive. After calling
         * this method the `subprocess.connected` and `process.connected` properties in
         * both the parent and child (respectively) will be set to `false`, and it will be
         * no longer possible to pass messages between the processes.
         *
         * The `'disconnect'` event will be emitted when there are no messages in the
         * process of being received. This will most often be triggered immediately after
         * calling `subprocess.disconnect()`.
         *
         * When the child process is a Node.js instance (e.g. spawned using {@link fork}), the `process.disconnect()` method can be invoked
         * within the child process to close the IPC channel as well.
         * @since v0.7.2
         */
        disconnect(): void;
        /**
         * By default, the parent will wait for the detached child to exit. To prevent the
         * parent from waiting for a given `subprocess` to exit, use the `subprocess.unref()` method. Doing so will cause the parent's event loop to not
         * include the child in its reference count, allowing the parent to exit
         * independently of the child, unless there is an established IPC channel between
         * the child and the parent.
         *
         * ```js
         * import { spawn } from 'node:child_process';
         *
         * const subprocess = spawn(process.argv[0], ['child_program.js'], {
         *   detached: true,
         *   stdio: 'ignore',
         * });
         *
         * subprocess.unref();
         * ```
         * @since v0.7.10
         */
        unref(): void;
        /**
         * Calling `subprocess.ref()` after making a call to `subprocess.unref()` will
         * restore the removed reference count for the child process, forcing the parent
         * to wait for the child to exit before exiting itself.
         *
         * ```js
         * import { spawn } from 'node:child_process';
         *
         * const subprocess = spawn(process.argv[0], ['child_program.js'], {
         *   detached: true,
         *   stdio: 'ignore',
         * });
         *
         * subprocess.unref();
         * subprocess.ref();
         * ```
         * @since v0.7.10
         */
        ref(): void;
    }

interface ChildProcess extends InternalEventEmitter<ChildProcessEventMap> {}

Constants

default

The default export, declared as crossSpawn.

The callable default, with the named exports hung off it.

compat-oracle re-exports default under the name 'module.exports', which is what a CommonJS require() of this module returns whole — so the vendored suite's const spawn = require('../../shim.mjs') gets this function and spawn.sync finds the property below, exactly as it does from cross-spawn itself.

const crossSpawn: typeof spawn & {
    spawn: typeof spawn;
    sync: typeof sync;
    parse: typeof parse;
    _parse: typeof parse;
    _enoent: {
        hookChildProcess: typeof hookChildProcess;
        verifyENOENT: typeof verifyENOENT;
        notFoundError: typeof notFoundError;
    };
};

_enoent

cross-spawn._enoent, the shape its dependants import.

const _enoent: {
    hookChildProcess: typeof hookChildProcess;
    verifyENOENT: typeof verifyENOENT;
    notFoundError: typeof notFoundError;
};

crossSpawn

The callable default, with the named exports hung off it.

compat-oracle re-exports default under the name 'module.exports', which is what a CommonJS require() of this module returns whole — so the vendored suite's const spawn = require('../../shim.mjs') gets this function and spawn.sync finds the property below, exactly as it does from cross-spawn itself.

const crossSpawn: typeof spawn & {
    spawn: typeof spawn;
    sync: typeof sync;
    parse: typeof parse;
    _parse: typeof parse;
    _enoent: {
        hookChildProcess: typeof hookChildProcess;
        verifyENOENT: typeof verifyENOENT;
        notFoundError: typeof notFoundError;
    };
};

module.exports

The callable default, with the named exports hung off it.

compat-oracle re-exports default under the name 'module.exports', which is what a CommonJS require() of this module returns whole — so the vendored suite's const spawn = require('../../shim.mjs') gets this function and spawn.sync finds the property below, exactly as it does from cross-spawn itself.

const crossSpawn: typeof spawn & {
    spawn: typeof spawn;
    sync: typeof sync;
    parse: typeof parse;
    _parse: typeof parse;
    _enoent: {
        hookChildProcess: typeof hookChildProcess;
        verifyENOENT: typeof verifyENOENT;
        notFoundError: typeof notFoundError;
    };
};

Interfaces

Parsed

What was asked for and what will be run. Mirrors cross-spawn's parsed exactly.

interface Parsed {
    command: string;
    args: string[];
    options: SpawnOptions;
    /**
     * The resolved executable, or `undefined` when nothing resolved. Windows-only, and the
     * flag `enoent.ts` reads: `cmd.exe` exits 1 for a command it could not find, which is
     * indistinguishable from a command that ran and failed unless somebody remembered whether
     * the file was there.
     */
    file: string | undefined;
    /** What the caller wrote, kept for the error message: it names their command, not ours. */
    original: {
        command: string;
        args: string[];
    };
}

SpawnOptions

Options a caller may pass through to child_process, plus the two this reads.

interface SpawnOptions {
    cwd?: string | undefined;
    env?: Record<string, string | undefined> | undefined;
    /**
     * Hand the whole thing to a shell. Off by default and **documented as the injection
     * surface it is**: with it on, an argument is text in a command line and a `;` or a `&`
     * in caller-supplied data is another command. Nothing in this package turns it on to
     * solve a Windows problem — that is what `escape.ts` is for.
     */
    shell?: boolean | string | undefined;
    /** `cross-spawn`'s own test hook: take the `cmd.exe` path even for a `.exe`. */
    forceShell?: boolean | undefined;
    windowsVerbatimArguments?: boolean | undefined;
    [key: string]: unknown;
}

SpawnSyncReturns

interface SpawnSyncReturns<T> {
        pid: number;
        output: Array<T | null>;
        stdout: T;
        stderr: T;
        status: number | null;
        signal: NodeJS.Signals | null;
        error?: Error;
    }

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