@npmcli/promise-spawn

Spawn processes the way the npm cli likes to do. Give it some options, it'll give you a Promise that resolves or rejects based on the results of the execution.

Note: When the current user is root, this will use infer-owner to find the owner of the current working directory, and run with that effective uid/gid. Otherwise, it runs as the current user always. (This helps prevent doing git checkouts and such, and leaving root-owned files lying around in user-owned locations.)

USAGE

const promiseSpawn = require('@npmcli/promise-spawn')

promiseSpawn('ls', [ '-laF', 'some/dir/*.js' ], {
  cwd: '/tmp/some/path', // defaults to process.cwd()
  stdioString: false, // stdout/stderr as strings rather than buffers
  stdio: 'pipe', // any node spawn stdio arg is valid here
  // any other arguments to node child_process.spawn can go here as well,
  // but uid/gid will be ignored and set by infer-owner if relevant.
}, {
  extra: 'things',
  to: 'decorate',
  the: 'result',
}).then(result => {
  // {code === 0, signal === null, stdout, stderr, and all the extras}
  console.log('ok!', result)
}).catch(er => {
  // er has all the same properties as the result, set appropriately
  console.error('failed!', er)
})

API

promiseSpawn(cmd, args, opts, extra) -> Promise

Run the command, return a Promise that resolves/rejects based on the process result.

Result or error will be decorated with the properties in the extra object. You can use this to attach some helpful info about why the command is being run, if it makes sense for your use case.

If stdio is set to anything other than 'inherit', then the result/error will be decorated with stdout and stderr values. If stdioString is set to true, these will be strings. Otherwise they will be Buffer objects.

Returned promise is decorated with the stdin stream if the process is set to pipe from stdin. Writing to this stream writes to the stdin of the spawned process.

Options

• stdioString Boolean, default false. Return stdout/stderr output as strings rather than buffers.
• cwd String, default process.cwd(). Current working directory for running the script. Also the argument to infer-owner to determine effective uid/gid when run as root on Unix systems.
• Any other options for child_process.spawn can be passed as well, but note that uid and gid will be overridden by the owner of the cwd when run as root on Unix systems, or null otherwise.