shelljs

What is shelljs?

ShellJS is a portable (Windows/Linux/OS X) implementation of Unix shell commands on top of the Node.js API. It provides the ability to script shell commands within JavaScript files and is used for tasks such as file manipulation, program execution, and script automation.

What are shelljs's main functionalities?

File Operations

ShellJS can perform file operations such as copying, removing, and moving files or directories.

const shell = require('shelljs');
shell.cp('-R', 'source_folder', 'destination_folder');
shell.rm('-rf', 'folder_to_delete');
shell.mv('old_file.txt', 'new_file.txt');

Executing Shell Commands

It can execute any shell command and capture its output.

const shell = require('shelljs');
let output = shell.exec('echo hello world', {silent:true}).stdout;
console.log(output);

Searching and Modifying Files

ShellJS can search for files that match a pattern and perform text replacement within files.

const shell = require('shelljs');
let files = shell.find('.').filter(file => file.match(/\.js$/));
shell.sed('-i', 'original_text', 'new_text', 'file.js');

Environment Variables

It allows manipulation of environment variables within a script.

const shell = require('shelljs');
shell.env['VAR_NAME'] = 'value';
console.log(shell.env['VAR_NAME']);

Directory Navigation

ShellJS can change the current working directory and get the present working directory.

const shell = require('shelljs');
shell.cd('path/to/directory');
console.log(shell.pwd().stdout);

Other packages similar to shelljs

child_process

This is a core Node.js module that allows you to execute shell commands and is more low-level compared to ShellJS. It does not provide the Unix shell command syntax, requiring more manual setup for cross-platform compatibility.

execa

Execa is a process execution tool that aims to be more feature-rich and have better Windows support than Node.js's child_process. It returns promises and can handle multiple processes simultaneously.

cross-spawn

Cross-spawn is a cross-platform solution for spawning child processes with command-line arguments. It normalizes Node.js issues on Windows and is used when you need to spawn processes with command-line arguments that are shell-friendly.

README

Shell.js - Unix shell commands for Node.js

Shell.js is a portable (Windows included) implementation of Unix shell commands for Node.js. It can be used to eliminate your project's dependencies on Unix while still keeping its familiar and powerful syntax.

The project is both unit-tested and battle-tested at Mozilla's pdf.js.

Example

require('shelljs/global');

// Copy files to release dir
mkdir('-p', 'out/Release');
cp('-R', 'lib/*.js', 'out/Release');

// Replace macros in each .js file
cd('lib');
for (file in ls('*.js')) {
  sed('-i', 'BUILD_VERSION', 'v0.1.2', file);
  sed('-i', /.*REMOVE_THIS_LINE.*\n/, '', file);
  sed('-i', /.*REPLACE_LINE_WITH_MACRO.*\n/, cat('macro.js'), file);
}
cd('..');

// Run external tool synchronously
if (exec('git commit -am "Auto-commit"').code !== 0) {
  echo('Error: Git commit failed');
  exit(1);
}

Global vs. Local

The example above uses the convenience script shelljs/global to reduce verbosity. If polluting your global namespace is not desirable, simply require shelljs.

Example:

var shell = require('shelljs');
shell.echo('hello world');

Make tool

A convenience script shelljs/make is also provided to mimic the behavior of a Unix Makefile. In this case all shell objects are global, and command line arguments will cause the script to execute only the corresponding function in the global target object. To avoid redundant calls, target functions are executed only once per script.

Example:

//
// Example file: make.js
//
require('shelljs/make');

target.all = function() {
  target.bundle();
  target.docs();
}

// Bundle JS files
target.bundle = function() {
  cd(__dirname);
  mkdir('build');
  cd('lib');
  cat('*.js').to('../build/output.js');
}

// Generate docs
target.docs = function() {
  cd(__dirname);
  mkdir('docs');
  cd('lib');
  for (file in ls('*.js')) {
    var text = grep('//@', file); // extract special comments
    text.replace('//@', ''); // remove comment tags
    text.to('docs/my_docs.md');
  }
}

To run the target all, call the above script without arguments: $ node make. To run the target docs: $ node make docs, and so on.

Installing

Via npm:

$ npm install shelljs

Or simply copy shell.js into your project's directory, and require() accordingly.

Commands reference

All commands run synchronously, unless otherwise stated.

cd('dir')

Changes to directory dir for the duration of the script

pwd()

Returns the current directory.

ls([options ,] path [,path ...])

ls([options ,] path_array)

Available options:

• -R: recursive
• -a: all files (include files beginning with .)

Examples:

ls('projs/*.js');
ls('-R', '/users/me', '/tmp');
ls('-R', ['/users/me', '/tmp']); // same as above

Returns list of files in the given path, or in current directory if no path provided. For convenient iteration via for (file in ls()), the format returned is a hash object: { 'file1':null, 'dir1/file2':null, ...}.

cp('[options ,] source [,source ...], dest')

cp('[options ,] source_array, dest')

Available options:

• -f: force
• -r, -R: recursive

Examples:

cp('file1', 'dir1');
cp('-Rf', '/tmp/*', '/usr/local/*', '/home/tmp');
cp('-Rf', ['/tmp/*', '/usr/local/*'], '/home/tmp'); // same as above

Copies files. The wildcard * is accepted.

rm([options ,] file [, file ...])

rm([options ,] file_array)

Available options:

• -f: force
• -r, -R: recursive

Examples:

rm('-rf', '/tmp/*');
rm('some_file.txt', 'another_file.txt');
rm(['some_file.txt', 'another_file.txt']); // same as above

Removes files. The wildcard * is accepted.

mv(source [, source ...], dest')

mv(source_array, dest')

Available options:

• f: force

Examples:

mv('-f', 'file', 'dir/');
mv('file1', 'file2', 'dir/');
mv(['file1', 'file2'], 'dir/'); // same as above

Moves files. The wildcard * is accepted.

mkdir([options ,] dir [, dir ...])

mkdir([options ,] dir_array)

Available options:

• p: full path (will create intermediate dirs if necessary)

Examples:

mkdir('-p', '/tmp/a/b/c/d', '/tmp/e/f/g');
mkdir('-p', ['/tmp/a/b/c/d', '/tmp/e/f/g']); // same as above

Creates directories.

cat(file [, file ...])

cat(file_array)

Examples:

var str = cat('file*.txt');
var str = cat('file1', 'file2');
var str = cat(['file1', 'file2']); // same as above

Returns a string containing the given file, or a concatenated string containing the files if more than one file is given (a new line character is introduced between each file). Wildcard * accepted.

'string'.to(file)

Examples:

cat('input.txt').to('output.txt');

Analogous to the redirection operator > in Unix, but works with JavaScript strings (such as those returned by cat, grep, etc). Like Unix redirections, to() will overwrite any existing file!

sed([options ,] search_regex, replace_str, file)

Available options:

• -i: Replace contents of 'file' in-place. Note that no backups will be created!

Examples:

sed('-i', 'PROGRAM_VERSION', 'v0.1.3', 'source.js');
sed(/.*DELETE_THIS_LINE.*\n/, '', 'source.js');

Reads an input string from file and performs a JavaScript replace() on the input using the given search regex and replacement string. Returns the new string after replacement.

grep(regex_filter, file [, file ...])

grep(regex_filter, file_array)

Examples:

grep('GLOBAL_VARIABLE', '*.js');

Reads input string from given files and returns a string containing all lines of the file that match the given regex_filter. Wildcard * accepted.

which(command)

Examples:

var nodeExec = which('node');

Searches for command in the system's PATH. On Windows looks for .exe, .cmd, and .bat extensions. Returns string containing the absolute path to the command.

echo(string [,string ...])

Examples:

echo('hello world');
var str = echo('hello world');

Prints string to stdout, and returns string with additional utility methods like .to().

exit(code)

Exits the current process with the given exit code.

env['VAR_NAME']

Object containing environment variables (both getter and setter). Shortcut to process.env.

exec(command [, options] [, callback])

Available options (all false by default):

• async: Asynchronous execution. Needs callback.
• silent: Do not echo program output to console.

Examples:

var version = exec('node --version', {silent:true}).output;

Executes the given command synchronously, unless otherwise specified. When in synchronous mode returns the object { code:..., output:... }, containing the program's output (stdout + stderr) and its exit code. Otherwise the callback gets the arguments (code, output).

Non-Unix commands

tempdir()

Searches and returns string containing a writeable, platform-dependent temporary directory. Follows Python's tempfile algorithm.

exists(path [, path ...])

exists(path_array)

Returns true if all the given paths exist.

error()

Tests if error occurred in the last command. Returns null if no error occurred, otherwise returns string explaining the error

verbose()

Enables all output (default)

silent()

Suppresses all output, except for explict echo() calls