Writing a Command Line Utility using Node

The article shows how to build a small command-line calculator with Node. It starts from a Grunt-init scaffold, adds a shebang line, links the package locally with npm link, and reads user input from process.argv before adding two values and printing the result.

It then extends the tool with package.json configuration for global installation, npm publishing steps, Commander.js for named options, Underscore.js for input checks, and a man page generated from README.md so users can run man calc.

Reading notes

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• Create the project with grunt-init node and review the generated files.
• Add preferGlobal and a bin entry in package.json so calc maps to lib/calc.js.
• Put #! /usr/bin/env node at the top of the script so Node executes it.
• Use npm link to install the package locally and test the command.
• Read arguments from process.argv.slice(2) and convert the values with parseInt.
• Add the two numbers and print the answer with console.log.
• Before publishing, authenticate with npm adduser, verify the repository settings, and run npm publish.
• Use commander to define named options like --number1 and --number2, then read them from program.number1 and program.number2.
• Use underscore to detect missing or invalid numeric values and print an error message when needed.
• Generate a manual with marked-man, add it to the man field in package.json, and view it with man calc.