Discussion Javascript

How to use shell commands in NodeJS based application.

updated on Leave a Comment on How to use shell commands in NodeJS based application.

Installing

Via npm:

$ npm install [-g] shelljs

Examples

var shell = require('shelljs'); if (!shell.which('git')) {   shell.echo('Sorry, this script requires git');   shell.exit(1); } // Copy files to release dir shell.rm('-rf', 'out/Release'); shell.cp('-R', 'stuff/', 'out/Release'); // Replace macros in each .js file shell.cd('lib'); shell.ls('*.js').forEach(function (file) {   shell.sed('-i', 'BUILD_VERSION', 'v0.1.2', file);   shell.sed('-i', /^.*REMOVE_THIS_LINE.*$/, '', file);   shell.sed('-i', /.*REPLACE_LINE_WITH_MACRO.*\n/, shell.cat('macro.js'), file); }); shell.cd('..'); // Run external tool synchronously if (shell.exec('git commit -am "Auto-commit"').code !== 0) {   shell.echo('Error: Git commit failed');   shell.exit(1); }
var shell = require('shelljs');

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

// Copy files to release dir
shell.rm('-rf', 'out/Release');
shell.cp('-R', 'stuff/', 'out/Release');

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

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

Exclude options

If you need to pass a parameter that looks like an option, you can do so like:

shell.grep('--', '-v', 'path/to/file'); // Search for "-v", no grep options

shell.cp('-R', '-dir', 'outdir'); // If already using an option, you're done

Global vs. Local

We no longer recommend using a global-import for ShellJS (i.e. require('shelljs/global')). While still supported for convenience, this pollutes the global namespace, and should therefore only be used with caution.

Instead, we recommend a local import (standard for npm packages):

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

Command reference

All commands run synchronously, unless otherwise stated. All commands accept standard bash globbing characters (*, ?, etc.), compatible with the node glob module.

For less-commonly used commands and features, please check out our wiki page.

cat([options,] file [, file …])

cat([options,] file_array)

Available options:

  • -n: number all output lines

Examples:

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

Returns a ShellString 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).

cd([dir])

Changes to directory dir for the duration of the script. Changes to home directory if no argument is supplied. Returns a ShellString to indicate success or failure.

chmod([options,] octal_mode || octal_string, file)

chmod([options,] symbolic_mode, file)

Available options:

  • -v: output a diagnostic for every file processed
  • -c: like verbose, but report only when a change is made
  • -R: change files and directories recursively

Examples:

chmod(755, '/Users/brandon');
chmod('755', '/Users/brandon'); // same as above
chmod('u+x', '/Users/brandon');
chmod('-R', 'a-w', '/Users/brandon');

Alters the permissions of a file or directory by either specifying the absolute permissions in octal form or expressing the changes in symbols. This command tries to mimic the POSIX behavior as much as possible. Notable exceptions:

  • In symbolic modes, a-r and -r are identical. No consideration is given to the umask.
  • There is no “quiet” option, since default behavior is to run silent.

Returns a ShellString indicating success or failure.

cp([options,] source [, source …], dest)

cp([options,] source_array, dest)

Available options:

  • -f: force (default behavior)
  • -n: no-clobber
  • -u: only copy if source is newer than dest
  • -r, -R: recursive
  • -L: follow symlinks
  • -P: don’t follow symlinks

Examples:

cp('file1', 'dir1');
cp('-R', 'path/to/dir/', '~/newCopy/');
cp('-Rf', '/tmp/*', '/usr/local/*', '/home/tmp');
cp('-Rf', ['/tmp/*', '/usr/local/*'], '/home/tmp'); // same as above

Copies files. Returns a ShellString indicating success or failure.

pushd([options,] [dir | ‘-N’ | ‘+N’])

Available options:

  • -n: Suppresses the normal change of directory when adding directories to the stack, so that only the stack is manipulated.
  • -q: Suppresses output to the console.

Arguments:

  • dir: Sets the current working directory to the top of the stack, then executes the equivalent of cd dir.
  • +N: Brings the Nth directory (counting from the left of the list printed by dirs, starting with zero) to the top of the list by rotating the stack.
  • -N: Brings the Nth directory (counting from the right of the list printed by dirs, starting with zero) to the top of the list by rotating the stack.

Examples:

// process.cwd() === '/usr'
pushd('/etc'); // Returns /etc /usr
pushd('+1');   // Returns /usr /etc

Save the current directory on the top of the directory stack and then cd to dir. With no arguments, pushd exchanges the top two directories. Returns an array of paths in the stack.

popd([options,] [‘-N’ | ‘+N’])

Available options:

  • -n: Suppress the normal directory change when removing directories from the stack, so that only the stack is manipulated.
  • -q: Supresses output to the console.

Arguments:

  • +N: Removes the Nth directory (counting from the left of the list printed by dirs), starting with zero.
  • -N: Removes the Nth directory (counting from the right of the list printed by dirs), starting with zero.

Examples:

echo(process.cwd()); // '/usr'
pushd('/etc');       // '/etc /usr'
echo(process.cwd()); // '/etc'
popd();              // '/usr'
echo(process.cwd()); // '/usr'

When no arguments are given, popd removes the top directory from the stack and performs a cd to the new top directory. The elements are numbered from 0, starting at the first directory listed with dirs (i.e., popd is equivalent to popd +0). Returns an array of paths in the stack.

dirs([options | ‘+N’ | ‘-N’])

Available options:

  • -c: Clears the directory stack by deleting all of the elements.
  • -q: Supresses output to the console.

Arguments:

  • +N: Displays the Nth directory (counting from the left of the list printed by dirs when invoked without options), starting with zero.
  • -N: Displays the Nth directory (counting from the right of the list printed by dirs when invoked without options), starting with zero.

Display the list of currently remembered directories. Returns an array of paths in the stack, or a single path if +N or -N was specified.

See also: pushd, popd

echo([options,] string [, string …])

Available options:

  • -e: interpret backslash escapes (default)
  • -n: remove trailing newline from output

Examples:

echo('hello world');
var str = echo('hello world');
echo('-n', 'no newline at end');

Prints string to stdout, and returns a ShellString.

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

Available options:

  • async: Asynchronous execution. If a callback is provided, it will be set to true, regardless of the passed value (default: false).
  • fatal: Exit upon error (default: false).
  • silent: Do not echo program output to console (default: false).
  • encoding: Character encoding to use. Affects the values returned to stdout and stderr, and what is written to stdout and stderr when not in silent mode (default: 'utf8').
  • and any option available to Node.js’s child_process.exec()

Examples:

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

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

exec('some_long_running_process', function(code, stdout, stderr) {
  console.log('Exit code:', code);
  console.log('Program output:', stdout);
  console.log('Program stderr:', stderr);
});

Executes the given command synchronously, unless otherwise specified. When in synchronous mode, this returns a ShellString. Otherwise, this returns the child process object, and the callback receives the arguments (code, stdout, stderr).

Not seeing the behavior you want? exec() runs everything through sh by default (or cmd.exe on Windows), which differs from bash. If you need bash-specific behavior, try out the {shell: 'path/to/bash'} option.

Security note: as shell.exec() executes an arbitrary string in the system shell, it is critical to properly sanitize user input to avoid command injection. For more context, consult the Security Guidelines.

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 a ShellString (with array-like properties) 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).

grep([options,] regex_filter, file [, file …])

grep([options,] regex_filter, file_array)

Available options:

  • -v: Invert regex_filter (only print non-matching lines).
  • -l: Print only filenames of matching files.
  • -i: Ignore case.

Examples:

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

Reads input string from given files and returns a ShellString containing all lines of the @ file that match the given regex_filter.

head([{‘-n’: <num>},] file [, file …])

head([{‘-n’: <num>},] file_array)

Available options:

  • -n <num>: Show the first <num> lines of the files

Examples:

var str = head({'-n': 1}, 'file*.txt');
var str = head('file1', 'file2');
var str = head(['file1', 'file2']); // same as above

Read the start of a file. Returns a ShellString.

ln([options,] source, dest)

Available options:

  • -s: symlink
  • -f: force

Examples:

ln('file', 'newlink');
ln('-sf', 'file', 'existing');

Links source to dest. Use -f to force the link, should dest already exist. Returns a ShellString indicating success or failure.

ls([options,] [path, …])

ls([options,] path_array)

Available options:

  • -R: recursive
  • -A: all files (include files beginning with ., except for . and ..)
  • -L: follow symlinks
  • -d: list directories themselves, not their contents
  • -l: list objects representing each file, each with fields containing ls -l output fields. See fs.Stats for more info

Examples:

ls('projs/*.js');
ls('-R', '/users/me', '/tmp');
ls('-R', ['/users/me', '/tmp']); // same as above
ls('-l', 'file.txt'); // { name: 'file.txt', mode: 33188, nlink: 1, ...}

Returns a ShellString (with array-like properties) of all the files in the given path, or files in the current directory if no path is provided.

mkdir([options,] dir [, dir …])

mkdir([options,] dir_array)

Available options:

  • -p: full path (and create intermediate directories, 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. Returns a ShellString indicating success or failure.

mv([options ,] source [, source …], dest’)

mv([options ,] source_array, dest’)

Available options:

  • -f: force (default behavior)
  • -n: no-clobber

Examples:

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

Moves source file(s) to dest. Returns a ShellString indicating success or failure.

pwd()

Returns the current directory as a ShellString.

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. Returns a ShellString indicating success or failure.

sed([options,] search_regex, replacement, file [, file …])

sed([options,] search_regex, replacement, file_array)

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');

Reads an input string from files, line by line, and performs a JavaScript replace() on each of the lines from the input string using the given search_regex and replacement string or function. Returns the new ShellString after replacement.

Note:

Like unix sed, ShellJS sed supports capture groups. Capture groups are specified using the $n syntax:

sed(/(\w+)\s(\w+)/, '$2, $1', 'file.txt');

Also, like unix sed, ShellJS sed runs replacements on each line from the input file (split by ‘\n’) separately, so search_regexes that span more than one line (or inlclude ‘\n’) will not match anything and nothing will be replaced.

set(options)

Available options:

  • +/-e: exit upon error (config.fatal)
  • +/-v: verbose: show all commands (config.verbose)
  • +/-f: disable filename expansion (globbing)

Examples:

set('-e'); // exit upon first error
set('+e'); // this undoes a "set('-e')"

Sets global configuration variables.

sort([options,] file [, file …])

sort([options,] file_array)

Available options:

  • -r: Reverse the results
  • -n: Compare according to numerical value

Examples:

sort('foo.txt', 'bar.txt');
sort('-r', 'foo.txt');

Return the contents of the files, sorted line-by-line as a ShellString. Sorting multiple files mixes their content (just as unix sort does).

tail([{‘-n’: <num>},] file [, file …])

tail([{‘-n’: <num>},] file_array)

Available options:

  • -n <num>: Show the last <num> lines of files

Examples:

var str = tail({'-n': 1}, 'file*.txt');
var str = tail('file1', 'file2');
var str = tail(['file1', 'file2']); // same as above

Read the end of a file. Returns a ShellString.

tempdir()

Examples:

var tmp = tempdir(); // "/tmp" for most *nix platforms

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

test(expression)

Available expression primaries:

  • '-b', 'path': true if path is a block device
  • '-c', 'path': true if path is a character device
  • '-d', 'path': true if path is a directory
  • '-e', 'path': true if path exists
  • '-f', 'path': true if path is a regular file
  • '-L', 'path': true if path is a symbolic link
  • '-p', 'path': true if path is a pipe (FIFO)
  • '-S', 'path': true if path is a socket

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 boolean value.

ShellString.prototype.to(file)

Examples:

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

Analogous to the redirection operator > in Unix, but works with ShellStrings (such as those returned by cat, grep, etc.). Like Unix redirections, to() will overwrite any existing file! Returns the same ShellString this operated on, to support chaining.

ShellString.prototype.toEnd(file)

Examples:

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

Analogous to the redirect-and-append operator >> in Unix, but works with ShellStrings (such as those returned by cat, grep, etc.). Returns the same ShellString this operated on, to support chaining.

touch([options,] file [, file …])

touch([options,] file_array)

Available options:

  • -a: Change only the access time
  • -c: Do not create any files
  • -m: Change only the modification time
  • {'-d': someDate}, {date: someDate}: Use someDate (instance of Date) instead of current time
  • {'-r': file}, {reference: file}: Use file‘s times instead of current time

Examples:

touch('source.js');
touch('-c', 'path/to/file.js');
touch({ '-r': 'referenceFile.txt' }, 'path/to/file.js');
touch({ date: new Date('December 17, 1995 03:24:00') }, 'path/to/file.js');

Update the access and modification times of each file to the current time. A file argument that does not exist is created empty, unless -c is supplied. This is a partial implementation of touch(1). Returns a ShellString indicating success or failure.

uniq([options,] [input, [output]])

Available options:

  • -i: Ignore case while comparing
  • -c: Prefix lines by the number of occurrences
  • -d: Only print duplicate lines, one for each group of identical lines

Examples:

uniq('foo.txt');
uniq('-i', 'foo.txt');
uniq('-cd', 'foo.txt', 'bar.txt');

Filter adjacent matching lines from input. Returns a ShellString.

which(command)

Examples:

var nodeExec = which('node');

Searches for command in the system’s PATH. On Windows, this uses the PATHEXT variable to append the extension if it’s not already executable. Returns a ShellString containing the absolute path to command.

exit(code)

Exits the current process with the given exit code.

error()

Tests if error occurred in the last command. Returns a truthy value if an error returned, or a falsy value otherwise.

Note: do not rely on the return value to be an error message. If you need the last error message, use the .stderr attribute from the last command’s return value instead.

ShellString(str)

Examples:

var foo = new ShellString('hello world');

This is a dedicated type returned by most ShellJS methods, which wraps a string (or array) value. This has all the string (or array) methods, but also exposes extra methods: .to(), .toEnd(), and all the pipe-able methods (ex. .cat(), .grep(), etc.). This can be easily converted into a string by calling .toString().

This type also exposes the corresponding command’s stdout, stderr, and return status code via the .stdout (string), .stderr (string), and .code (number) properties respectively.

env[‘VAR_NAME’]

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

Pipes

Examples:

grep('foo', 'file1.txt', 'file2.txt').sed(/o/g, 'a').to('output.txt');
echo('files with o\'s in the name:\n' + ls().grep('o'));
cat('test.js').exec('node'); // pipe to exec() call

Commands can send their output to another command in a pipe-like fashion. sed, grep, cat, exec, to, and toEnd can appear on the right-hand side of a pipe. Pipes can be chained.

Configuration

config.silent

Example:

var sh = require('shelljs');
var silentState = sh.config.silent; // save old silent state
sh.config.silent = true;
/* ... */
sh.config.silent = silentState; // restore old silent state

Suppresses all command output if true, except for echo() calls. Default is false.

config.fatal

Example:

require('shelljs/global');
config.fatal = true; // or set('-e');
cp('this_file_does_not_exist', '/dev/null'); // throws Error here
/* more commands... */

If true, the script will throw a Javascript error when any shell.js command encounters an error. Default is false. This is analogous to Bash’s set -e.

config.verbose

Example:

config.verbose = true; // or set('-v');
cd('dir/');
rm('-rf', 'foo.txt', 'bar.txt');
exec('echo hello');

Will print each command as follows:

cd dir/
rm -rf foo.txt bar.txt
exec echo hello

config.globOptions

Example:

config.globOptions = {nodir: true};

Use this value for calls to glob.sync() instead of the default options.

config.reset()

Example:

var shell = require('shelljs');
// Make changes to shell.config, and do stuff...
/* ... */
shell.config.reset(); // reset to original state
// Do more stuff, but with original settings
/* ... */

Reset shell.config to the defaults:

{
  fatal: false,
  globOptions: {},
  maxdepth: 255,
  noglob: false,
  silent: false,
  verbose: false,
}

Team

You may also like...

Blockchain Discussion Featured Lecture

Introduction to Hyperledger

Blockchain Discussion

ARK Blockchain

Discussion React.js

Datatables for React using Material-UI

Leave a Reply

Your email address will not be published. Required fields are marked *