Which for JS

Find the instances of an executable in the system path, implemented in JavaScript.

Requirements

The latest Node.js and npm versions. If you plan to play with the sources, you will also need the latest Gulp.js version.

Installing via npm

From a command prompt, run:

$ npm install --save @cedx/which

Usage

This package has an API based on Observables.

It provides a single function, which(), allowing to locate a command in the system path:

const {which} = require('@cedx/which');

which('foobar').subscribe(
  path => {
    // "path" is the absolute path to the executable.
    console.log(`The "foobar" command is located at: ${path}`);
  },
  error => {
    // The command was not found on the system path.
    console.log('The "foobar" command is not found.');
  }
);

Options

The which\which() function accepts three parameters:

• command: string: The command to be resolved.
• all: boolean = false: A value indicating whether to return all executables found, instead of just the first one.
• options: object = {}: The options to be passed to the underlying finder.

If you pass the true value as the second parameter, the function will return an array of all paths found, instead of only the first path found:

which('foobar', true).subscribe(paths => {
  console.log('The "foobar" command is located at:');
  for (let path of paths) console.log(path);
});

You can pass an options object as the third parameter:

• path: string|string[]: The system path, provided as a string or an array of directories. Defaults to the PATH environment variable.
• extensions: string|string[]: The executable file extensions, provided as a string or an array of file extensions. Defaults to the PATHEXT environment variable.
• pathSeparator: string: The character used to separate paths in the system path. Defaults to the path.delimiter constant.

The extensions option is only meaningful on the Windows platform, where the executability of a file is determined from its extension:

let options = {extensions: '.FOO;.EXE;.CMD'};
which('foobar', false, options).subscribe(path =>
  console.log(`The "foobar" command is located at: ${path}`);
);

Promise support

If you require it, an Observable can be converted to a Promise by using the toPromise() method:

let path = await which('foobar').toPromise();
console.log(`The "foobar" command is located at: ${path}`);

Command line interface

From a command prompt, install the which executable:

$ npm install --global @cedx/which

Then use it to find the instances of an executable:

$ which --help

  Usage: which [options] <command>

  Find the instances of an executable in the system path.

  Options:

    -v, --version  output the version number
    -a, --all      list all instances of executables found (instead of just the first one)
    -s, --silent   silence the output, just return the exit code (0 if any executable is found, otherwise 1)
    -h, --help     output usage information

For example:

$ which --all node

See also

• API reference
• Code coverage
• Continuous integration

License

Which for JS is distributed under the Apache License, version 2.0.