Synchronous child process calls for shell scripting (including CLI) in Node.js 0.10.x

Let's look at three options: the two mentioned in the question, plus execsync.

shelljs

shelljs is much more than a library for calling child processes. Primarily, it is a cross-platform JavaScript implementation of several POSIX utilities and shell builtins: >, cat, cd, chmod, cp, dirs, echo, env, exec, exit, find, grep, ln, ls, mkdir, mv, popd, pushd, pwd, rm, sed, test, which. It also provides a couple of useful functions of its own: error() and tempdir().

Its exec function can be used to run an external executable synchronously.

Syntax example

Using global namespace:

require('shelljs/global');var version = exec('node --version', {silent:true}).output;console.log('version ' + version);

Alternatively, using local namespace:

var sh = require('shelljs');var version = sh.exec('node --version', {silent:true}).output;console.log('version ' + version);

Key stats/specs

• Dependencies: 0
• Dependents: 411
• Downloads this month: 957851
• License: BSD*

Pros

• No dependencies.
• Can be used via global or local namespace at developer's discretion.
• Huge number of dependent packages and users, so likely to remain in use for some time.

Cons

• Cannot distinguish a called executable's output to stderr from its output to stdout. Bug?
• The shelljs documentation warns, "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."

exec-sync / execSync

exec-sync has been retired in favour of execSync. The rest of this section therefore refers to the latter.

The execSync library consists of a JavaScript wrapper around a C++ core. During the installation of execSync, the C++ core is compiled into a platform-appropriate NodeJS binary module.

Syntax example

var sh = require('execSync');var version = sh.exec('node --version').stdout;console.log('version ' + version);

Key stats/specs

• Dependencies: 1
• Dependents: 91
• Downloads this month: 20525
• License: MIT

Pros

• Straightforward once installed.
• Large number of dependent packages and users, so likely to remain in use for some time.

Cons

• Not dependency-free.
• Installation requires the presence of a C++ compiler.
• Cannot distinguish a called executable's output to stderr from its output to stdout. Bug?

execsync

Worth mentioning here as it is easily confused with execSync (see above) by any case-insensitive search engine, other algorithm, or human. Confusing matters further, the author of execsync has used the orthography "execSync" at a few points in execsync's code and documentation.

Like execSync above, the execsync library consists of a JavaScript wrapper around a C++ core. During the installation of execsync, the C++ core is compiled into a platform-appropriate NodeJS binary module.

Syntax example

var sh = require('execsync');var version = sh('node --version');console.log('version ' + version);

Key stats/specs

• Dependencies: 0
• Dependents: 3
• Downloads this month: 20233
• License: NYSL

Pros

• No dependencies.

Cons

• Inconsistent internal orthography.
• Installation requires the presence of a C++ compiler.
• Documentation is in Japanese (not a "con" for everyone, admittedly).
• Cannot distinguish a called executable's output to stderr from its output to stdout.
• Small number of dependents, so presumably less entrenched in Node.js community.