main

node-main

Runs a block of code if a script is called directly as in calling node script. It will not call the block of code if the script has been required in another module as in require('script').

node-main utilizes optimist for argument parsing and provides other tools that are useful for when working with command line scripts.

Installation & Usage

npm install --save main

require('main')

Once required, you can chain the functions below

.usage(message)

An optional message to append to the top of flags that can describe how the script should be invoked, e.g.

Usage: ./script [flags] <posArg1> <posArg2>

Flags do not have to be specified in this string. Usage for flags are automatically generated based on the options provided (see below) and will appear after this usage message.

.flags(options)

options follows the optimist format for options, but groups them together, e.g.:

require('main').flags({
    f: { alias: 'flag' },
    t: { alias: 'secondFlag' },
    d: { demand: true },
    // ...
})

.run(fn)

fn is the callback that will be invoked when the script is ran directly from a terminal. It can take the following parameters:

fn(argv, exit, help)

• argv is the parsed optimist argv object
• exit is a helper function that can be used to exit the script. It follows the form exit(exitCode, optionalMessage). If no exit code if provided, it will exit with 0 (success).
• help is the usage information if the need arises to explicitly display it.

Example

Refer to the following script as sentence.js

#!/usr/bin/env node

exports.sentence = function(name, word1, word2) {
    return name + ',' + word1 + ' ' + word2 + '.';
};

require('main')
.usage('Usage:\n node test.js [flags] <word1> <word2>')
.flags({
    n: { alias: 'name', demand: true }
})
.run(function(argv, exit, help) {
    // exit if there aren't two words (positional arguments)
    if (argv._.length !== 2) { exit(1, help); }
    var word1 = argv._[0],
        word2 = argv._[1];
    exports.sentence(argv.name, word1, word2);
});

Running from the terminal ($? indicates exit status):

> node sentence.js --name Nolan sit down
Nolan, sit down.
> $?
0 (success)
> node sentence.js
# (prints out help & usage information. name / words are not defined)
> $?
1 (failure)

Using the module from another script will not execute the code in main:

var scriptAbove = require('./scriptAbove');
console.log(scriptAbove.sentence('Nolan', 'sit', 'down'));

Note

When installing, make sure to use the --save option and/or specify the version in your package.json dependencies. This package is undergoing some heavy changes at the moment and new versions may be radically different from previous releases. This type of business will stop once it reaches 0.1.0.