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

ShellJS - Unix shell commands for Node.js

• This project is young and experimental. Use at your own risk.
• Major API change as of v0.0.4: ls() and find() now return arrays.

ShellJS is a portable (Windows included) implementation of Unix shell commands on top of the Node.js API. You can use it to eliminate your shell script's dependency on Unix while still keeping its familiar and powerful commands.

The project is unit-tested and is being used at Mozilla's PDF.js, Butter.js and others.

Examples

JavaScript

require('shelljs/global');

if (!which('git')) {
  echo('Sorry, this script requires git');
  exit(1);
}

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

// Replace macros in each .js file
cd('lib');
ls('*.js').forEach(function(file) {
  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);
}

CoffeeScript

require 'shelljs/global'

if not which 'git'
  echo 'Sorry, this script requires git'
  exit 1

# Copy files to release dir
mkdir '-p', 'out/Release'
cp '-R', 'stuff/*', '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 (CoffeeScript):

require 'shelljs/make'

target.all = ->
  target.bundle()
  target.docs()

target.bundle = ->
  cd __dirname
  mkdir 'build'
  cd 'lib'
  (cat '*.js').to '../build/output.js'

target.docs = ->
  cd __dirname
  mkdir 'docs'
  cd 'lib'
  for file in ls '*.js'
    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 [-g] shelljs

If the global option -g is specified, the binary sjs will be installed. This makes it possible to run ShellJS scripts much like any shell script from the command line, i.e. without requiring a node_modules folder:

$ sjs my_script

You can also just copy shell.js into your project's directory, and require() accordingly.

Command 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 array of files in the given path, or in current directory if no path provided.

find(path [,path ...])

find(path_array)

Examples:

find('src', 'lib');
find(['src', 'lib']); // same as above
find('.').filter(function(file) { return file.match(/\.js$/); });

Returns array of all files (however deep) in the given paths.

The main difference from ls('-R', path) is that the resulting file names include the base directories, e.g. lib/resources/file1 instead of just file1.

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.

test(expression)

Available expression primaries:

• '-d', 'path': true if path is a directory
• '-f', 'path': true if path is a regular file

Examples:

if (test('-d', path)) { /* do something with dir */ };
if (!test('-f', path)) continue; // skip if it's a regular file

Evaluates expression using the available primaries and returns corresponding value.

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

grep([options ,] regex_filter, file_array)

Available options:

• -v: Inverse the sense of the regex and print the lines not matching the criteria.

Examples:

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

var child = exec('some_long_running_process', {async:true});
child.stdout.on('data', function(data) { 
  /* ... do something with data ... */ 
});

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 returns the child process object, and the callback gets the arguments (code, output).

Note: For long-lived processes, it's best to run exec() asynchronously as the current synchronous implementation uses a lot of CPU. This should be getting fixed soon.

Non-Unix commands

tempdir()

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

error()

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

silent([state])

Example:

var silentState = silent();
silent(true);
/* ... */
silent(silentState); // restore old silent state

Suppresses all command output if state = true, except for echo() calls. Returns state if no arguments given.

Deprecated

exists(path [, path ...])

exists(path_array)

This function is being deprecated. Use test() instead.

Returns true if all the given paths exist.

verbose()

This function is being deprecated. Use silent(false) instead.

Enables all output (default)