process-promises

Node child processes as promises

Installation

npm install process-promises --save

exec

Runs a command in a shell and buffers the output.

Usage - TypeScript

import { exec } from 'process-promises';

exec('node ./node_modules/gulp/bin/gulp.js default')
    .on('process', process => console.log('Pid: ', process.pid))
    .then(result => {
        console.log('stdout: ', result.stdout);
        console.log('stderr: ', result.stderr);
    })
    .fail(err => {
        console.error('ERROR: ', err);
    });

Usage - JavaScript

var exec = require('process-promises').exec;

exec('node ./node_modules/gulp/bin/gulp.js default')
    .on('process', function(process) {
        console.log('Pid: ', process.pid); 
    })
    .then(function (result) {
        console.log('stdout: ', result.stdout);
        console.log('stderr: ', result.stderr);
    })
    .fail(function (err) {
        console.error('ERROR: ', err);
    });

Syntax

/**
 * Runs a command in a shell and buffers the output.
 * @param command {string} - The command
 * @param options {ExecOptions} - Options
 * @returns {PromiseWithEvents<ExecResult>}
 * @see {@link https://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback}
 */
function exec(command: string, options?: ExecOptions): PromiseWithEvents<ExecResult>;

interface ExecOptions {
    /** Current working directory of the child process */
    cwd?: string;
    /** Object Environment key-value pairs */
    env?: any;
    /** Encoding - default: 'utf8' */
    encoding?: string;
    /**
     * Shell to execute the command with (Default: '/bin/sh' on UNIX, 'cmd.exe' on Windows, The shell
     * should understand the -c switch on UNIX or /s /c on Windows. On Windows, command line parsing
     * should be compatible with cmd.exe.)
     */
    shell?: string;
    /** Time out - default: 0 */
    timeout?: number;
    /**
     * Largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is
     * killed - default: 200*1024
     */
    maxBuffer?: number;
    /** Kill signal - default: 'SIGTERM' */
    killSignal?: string;
}

interface ExecResult {
    /** The standard output emitted from the process as a string */
    stdout: string;
    /** The standard error emitted from the process as a string */
    stderr: string;
}

execFile

This is similar to exec() except it does not execute a subshell but rather the specified file directly. This makes it slightly leaner than exec().

Usage - TypeScript

import { execFile } from 'process-promises';

execFile(process.execPath, ['./node_modules/gulp/bin/gulp.js', 'default'])
    .on('process', process => console.log('Pid: ', process.pid))
    .then(result => {
        console.log('stdout: ', result.stdout);
        console.log('stderr: ', result.stderr);
    })
    .fail(err => {
        console.error('ERROR: ', err);
    });

Usage - JavaScript

var execFile = require('process-promises').execFile;

execFile(process.execPath, ['./node_modules/gulp/bin/gulp.js', 'default'])
    .on('process', function(process) {
        console.log('Pid: ', process.pid); 
    })
    .then(function (result) {
        console.log('stdout: ', result.stdout);
        console.log('stderr: ', result.stderr);
    })
    .fail(function (err) {
        console.error('ERROR: ', err);
    });

Syntax

/**
 * This is similar to exec() except it does not execute a subshell but rather the specified
 * file directly. This makes it slightly leaner than exec().
 * @param file {string} - The file to execute
 * @param args {string[]} - List of string arguments
 * @param options {ExecFileOptions} - Options
 * @returns {PromiseWithEvents<ExecResult>}
 * @see {@link https://nodejs.org/api/child_process.html#child_process_child_process_execfile_file_args_options_callback}
 */
function execFile(file: string, options?: ExecFileOptions): PromiseWithEvents<ExecResult>;
function execFile(file: string, args?: string[], options?: ExecFileOptions): PromiseWithEvents<ExecResult>;

interface ExecFileOptions {
    /** Current working directory of the child process */
    cwd?: string;
    /** Object Environment key-value pairs */
    env?: any;
    /** Encoding - default: 'utf8' */
    encoding?: string;
    /** Time out - default: 0 */
    timeout?: number;
    /**
     * Largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is
     * killed - default: 200*1024
     */
    maxBuffer?: number;
    /** Kill signal - default: 'SIGTERM' */
    killSignal?: string;
}

interface ExecResult {
    /** The standard output emitted from the process as a string */
    stdout: string;
    /** The standard error emitted from the process as a string */
    stderr: string;
}

spawn

Launches a new process with the given command, with command line arguments in args. If omitted, args defaults to an empty Array.

Usage - TypeScript

import { spawn } from 'process-promises';

spawn(process.execPath, ['./node_modules/gulp/bin/gulp.js', 'default'])
    .on('process', process => console.log('Pid: ', process.pid))
    .on('stdout', line => console.log('stdout: ', line))
    .on('stderr', line => console.log('stderr: ', line))
    .then(result => {
        console.log('Exit code: ' + result.exitCode);
    })
    .fail(err => {
        console.error('ERROR: ', err);
    });

Usage - JavaScript

var execFile = require('process-promises').execFile;

spawn(process.execPath, ['./node_modules/gulp/bin/gulp.js', 'default'])
    .on('process', function(process) {
        console.log('Pid: ', process.pid);
    })
    .on('stdout', function(line) {
        console.log('stdout: ', line); 
    })
    .on('stderr', function(line) {
        console.log('stdout: ', line); 
    })
    .then(function (result) {
        console.log('Exit code: ' + result.exitCode);
    })
    .fail(function (err) {
        console.error('ERROR: ', err);
    });

Syntax

/**
 * Launches a new process with the given command, with command line arguments in args. If
 * omitted, args defaults to an empty Array.
 * @param command {string} - The file to execute
 * @param args {string[]} - List of string arguments
 * @param options {SpawnOptions} - Options
 * @returns {PromiseWithEvents<SpawnResult>}
 * @see {@link https://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options}
 */
function spawn(command: string, options?: SpawnOptions): PromiseWithEvents<SpawnResult>;
function spawn(command: string, args?: string[], options?: SpawnOptions): PromiseWithEvents<SpawnResult>;

interface SpawnOptions {
    /** Current working directory of the child process */
    cwd?: string;
    /** Object Environment key-value pairs */
    env?: any;
    /**
     * Child's stdio configuration
     * @see {@link https://nodejs.org/api/child_process.html#child_process_options_stdio}
     */
    stdio?: string | [
        string | NodeJS.WritableStream | number,
        string | NodeJS.ReadableStream | number,
        string | NodeJS.ReadableStream | number
    ];
    /**
     * Prepare child to run independently of its parent process. Specific behavior depends on the platform
     * @see {@link https://nodejs.org/api/child_process.html#child_process_options_detached}
     */
    detached?: boolean;
}

interface SpawnResult {
    /** The exit code, if the process exited normally. */
    exitCode: number;
}

fork

Launches a new node process with the given module, with command line arguments in args. If omitted, args defaults to an empty Array.

The module is resolved using the node require.resolve() algorithm

This function calls spawn - not child_process.fork

Usage - TypeScript

import { fork } from 'process-promises';

fork('gulp/bin/gulp.js', ['default'])
    .on('process', process => console.log('Pid: ', process.pid))
    .on('stdout', line => console.log('stdout: ', line))
    .on('stderr', line => console.log('stderr: ', line))
    .then(result => {
        console.log('Exit code: ' + result.exitCode);
    })
    .fail(err => {
        console.error('ERROR: ', err);
    });

Usage - JavaScript

var execFile = require('process-promises').execFile;

fork('gulp/bin/gulp.js', ['default'])
    .on('process', function(process) {
        console.log('Pid: ', process.pid);
    })
    .on('stdout', function(line) {
        console.log('stdout: ', line); 
    })
    .on('stderr', function(line) {
        console.log('stdout: ', line); 
    })
    .then(function (result) {
        console.log('Exit code: ' + result.exitCode);
    })
    .fail(function (err) {
        console.error('ERROR: ', err);
    });

Syntax

/**
 * Launches a new node process with the given module, with command line arguments in args. If
 * omitted, args defaults to an empty Array.
 * The module is resolved using the {@link http://nodejs.org/docs/v0.4.8/api/all.html#all_Together|node require.resolve() algorithm}
 * This function calls spawn - not {@link https://nodejs.org/api/child_process.html#child_process_child_process_fork_modulepath_args_options|child_process.fork}
 * @param modulePath {string} - The module to execute with node
 * @param args {string[]} - List of string arguments
 * @param options {SpawnOptions} - Options
 * @returns {PromiseWithEvents<SpawnResult>}
 * @see {@link https://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options}
 */
function fork(modulePath: string, options?: SpawnOptions): PromiseWithEvents<SpawnResult>;
function fork(modulePath: string, args?: string[], options?: SpawnOptions): PromiseWithEvents<SpawnResult>;

interface SpawnOptions {
    /** Current working directory of the child process */
    cwd?: string;
    /** Object Environment key-value pairs */
    env?: any;
    /**
     * Child's stdio configuration
     * @see {@link https://nodejs.org/api/child_process.html#child_process_options_stdio}
     */
    stdio?: string | [
        string | NodeJS.WritableStream | number,
        string | NodeJS.ReadableStream | number,
        string | NodeJS.ReadableStream | number
    ];
    /**
     * Prepare child to run independently of its parent process. Specific behavior depends on the platform
     * @see {@link https://nodejs.org/api/child_process.html#child_process_options_detached}
     */
    detached?: boolean;
}

interface SpawnResult {
    /** The exit code, if the process exited normally. */
    exitCode: number;
}