# Build Your Own Node.js CLI Package
![GIF](https://media.giphy.com/media/yR4xZagT71AAM/giphy.gif)
## Coverage * Node.js CLI first principles * Frameworks * Configuration * Distribution
## Principles of CLI
### Node.js Scripting Running an event loop to completion or interruption
### Interactive / Session Great for destructive or constructive actions `command (begin session)`
### Single Command Great for compositional, single-purpose scripts `command [arguments]` ```bash $ ls -l -a total 24 drwxr-xr-x 6 Josh staff 204 Jul 26 2017 . drwxr-xr-x 6 Josh staff 204 Aug 10 2017 .. drwxr-xr-x 15 Josh staff 510 Apr 15 17:26 .git -rw-r--r-- 1 Josh staff 1061 Jul 26 2017 LICENSE -rw-r--r-- 1 Josh staff 1030 Jul 26 2017 README.md -rwxr-xr-x 1 Josh staff 1190 Jul 26 2017 heroku_multi ```
### Multiple Commands More like complete applications `prefix command [arguments]` ```bash $ git log --pretty=format:%s new:usr: Add initial working version Initial commit $ git status On branch master Your branch is up to date with 'origin/master'. ```
### What makes Node.js a good candidate? * Widely available * Event Loop can be a benefit * Forked processes can be a benefit * Distribution is wickedly simple/fast
## Communicating to Node.js Scripts
### What's in a `process`? Your script always operates in context ```js process { title: 'node', version: 'v8.1.2', moduleLoadList: [ 'Binding contextify', 'Binding natives', 'Binding config', 'NativeModule events', 'Binding async_wrap', 'Binding icu', 'NativeModule util', 'Binding uv', 'NativeModule buffer', 'Binding buffer', 'Binding util', 'NativeModule internal/util', 'NativeModule internal/errors', 'Binding constants', 'NativeModule internal/buffer', 'NativeModule timers', 'Binding timer_wrap', 'NativeModule internal/linkedlist', 'NativeModule async_hooks', 'NativeModule assert', 'NativeModule internal/process', 'NativeModule internal/process/warning', 'NativeModule internal/process/next_tick', 'NativeModule internal/process/promises', 'NativeModule internal/process/stdio', 'NativeModule internal/url', 'NativeModule internal/querystring', 'NativeModule querystring', 'Binding url', 'NativeModule path', 'NativeModule module', 'NativeModule internal/module', 'NativeModule vm', 'NativeModule fs', 'Binding fs', 'NativeModule stream', 'NativeModule internal/streams/legacy', 'NativeModule _stream_readable', 'NativeModule internal/streams/BufferList', 'NativeModule internal/streams/destroy', 'NativeModule _stream_writable', 'NativeModule _stream_duplex', 'NativeModule _stream_transform', 'NativeModule _stream_passthrough', 'Binding fs_event_wrap', 'NativeModule internal/fs', 'NativeModule console', 'Binding tty_wrap', 'NativeModule tty', 'NativeModule net', 'NativeModule internal/net', 'Binding cares_wrap', 'Binding tcp_wrap', 'Binding pipe_wrap', 'Binding stream_wrap', 'Binding signal_wrap', 'Binding inspector' ], versions: { http_parser: '2.7.0', node: '8.1.2', v8: '5.8.283.41', uv: '1.12.0', zlib: '1.2.11', ares: '1.10.1-DEV', modules: '57', openssl: '1.0.2l', icu: '59.1', unicode: '9.0', cldr: '31.0.1', tz: '2017b' }, arch: 'x64', platform: 'darwin', release: { name: 'node', sourceUrl: 'https://nodejs.org/download/release/v8.1.2/node-v8.1.2.tar.gz', headersUrl: 'https://nodejs.org/download/release/v8.1.2/node-v8.1.2-headers.tar.gz' }, argv: [ '/usr/local/bin/node', '/Users/Joshua/src/foo.js' ], execArgv: [], env: { TERM_PROGRAM: 'Apple_Terminal', ANDROID_HOME: '/Users/Joshua/Library/Android/sdk', TERM: 'xterm-256color', SHELL: '/bin/bash', CLICOLOR: '1', TMPDIR: '/var/folders/0c/1xh24_cd64z0qgdyhrrhqmzm0000gp/T/', Apple_PubSub_Socket_Render: '/private/tmp/com.apple.launchd.xzSg211msb/Render', TERM_PROGRAM_VERSION: '404', USER: 'Joshua', SSH_AUTH_SOCK: '/private/tmp/com.apple.launchd.I8BfXr2o6k/Listeners', PATH: '/Users/Joshua/.cargo/bin:~/Library/Android/sdk/tools:~/Library/Android/sdk/platform-tools:/Library/Frameworks/Python.framework/Versions/2.7/bin:/usr/local/bin:/usr/local/share/npm/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/go/bin:/opt/X11/bin:/usr/local/git/bin:/Users/Joshua/.rvm/bin:/Users/Joshua/projects/golang/bin:/Users/Joshua/bin', PWD: '/Users/Joshua/src', EDITOR: 'vim', LANG: 'en_US.UTF-8', XPC_FLAGS: '0x0', XPC_SERVICE_NAME: '0', HOME: '/Users/Joshua', SHLVL: '1', PYTHONPATH: '/usr/local/lib/python2.7/site-packages:', LOGNAME: 'Joshua', GOPATH: '/Users/Joshua/projects/golang', PKG_CONFIG_PATH: '/opt/local/lib/pkgconfig:', DISPLAY: '/private/tmp/com.apple.launchd.Vdwo7PHHuC/org.macosforge.xquartz:0', SECURITYSESSIONID: '186a6', OLDPWD: '/Users/Joshua/src/github.com/andjosh/andjosh.github.io', _: '/usr/local/bin/node', __CF_USER_TEXT_ENCODING: '0x1F6:0x0:0x0' }, pid: 99573, features: { debug: false, uv: true, ipv6: true, tls_npn: true, tls_alpn: true, tls_sni: true, tls_ocsp: true, tls: true }, _needImmediateCallback: false, execPath: '/usr/local/bin/node', debugPort: 9229, _startProfilerIdleNotifier: [Function: _startProfilerIdleNotifier], _stopProfilerIdleNotifier: [Function: _stopProfilerIdleNotifier], _getActiveRequests: [Function: _getActiveRequests], _getActiveHandles: [Function: _getActiveHandles], reallyExit: [Function: reallyExit], abort: [Function: abort], chdir: [Function: chdir], cwd: [Function: cwd], umask: [Function: umask], getuid: [Function: getuid], geteuid: [Function: geteuid], setuid: [Function: setuid], seteuid: [Function: seteuid], setgid: [Function: setgid], setegid: [Function: setegid], getgid: [Function: getgid], getegid: [Function: getegid], getgroups: [Function: getgroups], setgroups: [Function: setgroups], initgroups: [Function: initgroups], _kill: [Function: _kill], _debugProcess: [Function: _debugProcess], _debugPause: [Function: _debugPause], _debugEnd: [Function: _debugEnd], hrtime: [Function: hrtime], cpuUsage: [Function: cpuUsage], dlopen: [Function: dlopen], uptime: [Function: uptime], memoryUsage: [Function: memoryUsage], binding: [Function: binding], _linkedBinding: [Function: _linkedBinding], _setupDomainUse: [Function: _setupDomainUse], _events: { warning: [Function], newListener: [Function], removeListener: [Function], SIGWINCH: [Function] }, _rawDebug: [Function], _eventsCount: 4, domain: null, _maxListeners: undefined, _fatalException: [Function], _exiting: false, assert: [Function], config: { target_defaults: { cflags: [], default_configuration: 'Release', defines: [], include_dirs: [], libraries: [] }, variables: { asan: 0, coverage: false, debug_devtools: 'node', force_dynamic_crt: 0, host_arch: 'x64', icu_data_file: 'icudt59l.dat', icu_data_in: '../../deps/icu-small/source/data/in/icudt59l.dat', icu_endianness: 'l', icu_gyp_path: 'tools/icu/icu-generic.gyp', icu_locales: 'en,root', icu_path: 'deps/icu-small', icu_small: true, icu_ver_major: '59', llvm_version: 0, node_byteorder: 'little', node_enable_d8: false, node_enable_v8_vtunejit: false, node_install_npm: true, node_module_version: 57, node_no_browser_globals: false, node_prefix: '/', node_release_urlbase: 'https://nodejs.org/download/release/', node_shared: false, node_shared_cares: false, node_shared_http_parser: false, node_shared_libuv: false, node_shared_openssl: false, node_shared_zlib: false, node_tag: '', node_use_bundled_v8: true, node_use_dtrace: true, node_use_etw: false, node_use_lttng: false, node_use_openssl: true, node_use_perfctr: false, node_use_v8_platform: true, node_without_node_options: false, openssl_fips: '', openssl_no_asm: 0, shlib_suffix: '57.dylib', target_arch: 'x64', uv_parent_path: '/deps/uv/', uv_use_dtrace: true, v8_enable_gdbjit: 0, v8_enable_i18n_support: 1, v8_enable_inspector: 1, v8_no_strict_aliasing: 1, v8_optimized_debug: 0, v8_promise_internal_field_count: 1, v8_random_seed: 0, v8_use_snapshot: true, want_separate_host_toolset: 0, want_separate_host_toolset_mkpeephole: 0, xcode_version: '7.0' } }, emitWarning: [Function], nextTick: [Function: nextTick], _tickCallback: [Function: _tickCallback], _tickDomainCallback: [Function: _tickDomainCallback], stdout: [Getter], stderr: [Getter], stdin: [Getter], openStdin: [Function], exit: [Function], kill: [Function], argv0: 'node', mainModule: Module { id: '.', exports: {}, parent: null, filename: '/Users/Joshua/src/foo.js', loaded: false, children: [], paths: [ '/Users/Joshua/src/node_modules', '/Users/Joshua/node_modules', '/Users/node_modules', '/node_modules' ] } } ```
### Executing with environment variables Pervasive, global, shared Like cues, rather than directives
### Executing with flags/argv Specific, pedantic Like directives, rather than cues _Will exclude node-specific flags placed before the script name._
### Standard Input Powerful in conjunction with others Data, rather than directive
### Placement Matters ```bash # $ [env] node [node-flags] <script> [argv] # [stdin] # ```
## Frameworks
### Interactive / Session [flatiron/prompt](https://github.com/flatiron/prompt) A beautiful command-line prompt for node.js * Simple, familiar API
```js var prompt = require('prompt'); prompt.start(); prompt.get(['username', 'email'], function (err, result) { console.log('Command-line input received:'); console.log(' username: ' + result.username); console.log(' email: ' + result.email); }); ``` ```sh $ node examples/simple-prompt.js prompt: username: some-user prompt: email: [email protected] Command-line input received: username: some-user email: [email protected] ```
### Session & Args [esatterwhite/node-seeli](https://github.com/esatterwhite/node-seeli) Object orientated, event driven CLI module * Handles both interactive and directive * Heavy up-front configuration * Allows for heavily automated parsing * Emits events
```js const os = require('os'); const cli = require('seeli'); cli.set({ exitOnError: true , color: 'green' , name: 'example' }); const Hello = new cli.Command({ description:"displays a simple hello world command" , name: 'hello' , ui: 'dots' , usage:[ `${cli.bold("Usage:")} ${cli.get('name')} hello --interactive` , `${cli.bold("Usage:")} ${cli.get('name')} hello --name=john` , `${cli.bold("Usage:")} ${cli.get('name')} hello --name=john --name=marry --name=paul -v screaming` ] , flags:{ name:{ type:[ String, Array ] , shorthand:'n' , description:"The name of the person to say hello to" , required:true } , volume:{ type:String , choices:['normal', 'screaming'] , description:"Will yell at each person" , default:'normal' , shorthand:'v' } } , onContent: (content) => { console.log(content.join(os.EOL)) } , run: async function( cmd, data ){ const out = []; this.ui.start('processing names'); var names = Array.isArray( data.name ) ? data.name : [ data.name ]; for( var x = 0; x< names.length; x++ ){ this.ui.text = (`processing ${names[x]}`) let value = "Hello, " + names[x]; out.push( data.volume === 'screaming' ? value.toUpperCase() : value ); } this.ui.succeed('names processed successfully'); return out } }); cli.use('hello', Hello); cli.run(); ```
![Example seeli GIF](https://raw.githubusercontent.com/esatterwhite/node-seeli/master/assets/seeli.gif)
### Argument-Based [tj/commander.js](https://github.com/tj/commander.js#readme) Node.js command-line interfaces made easy * No dependencies * As simple as possible * Lends itself to more complex CLIs
```js var program = require('commander'); program .option('--no-sauce', 'Remove sauce') .option('--topping', 'The good parts', 'cheese') .parse(process.argv); console.log(`you ordered a ${program.topping} pizza`); if (program.sauce) console.log(' with sauce'); else console.log(' without sauce'); ``` ```bash $ node index.js --topping green you ordered a green pizza with sauce $ node index.js --no-saouce you ordered a cheese pizza without sauce ```
### Arguments & Meta-CLI [heroku/oclif](https://github.com/oclif/oclif) Node.js Open CLI Framework. Built with 💜 by Heroku. * Argument parsing * Command structure, generation * Testing helpers * Plugins * Hooks * Optional Typescript * Brand new
```js const {Command, flags} = require('@oclif/command'); class OclifExampleSingleJsCommand extends Command { async run() { const {flags} = this.parse(OclifExampleSingleJsCommand); const name = flags.name || 'world'; this.log(`hello ${name} from ./src/index.js`); } } OclifExampleSingleJsCommand.flags = { version: flags.version({char: 'v'}), help: flags.help({char: 'h'}), name: flags.string({char: 'n', description: 'name to print'}), }; ``` ```bash $ node index.js hello world from ./src/index.js $ node index.js --name foobar hello foobar from ./src/index.js ```
## Configuration & Settings
### Avoid If Possible CI build scripts probably don't need much * Standard input * Environment variables * Arguments
### Persistent State Daily interactive scripts can benefit from pre-configuration * Authentication * Preferences * Aliases
### Config / Dot Files * Default empty * Loading * Saving * Upgrading / Migrating * Be a good neighbor
### Where to Load? * Root vs. local config files ```js const path = require('path'); const os = require('os'); const pkg = require('../../package.json'); const rootConfig = path.resolve(os.homedir(), '.' + pkg.name, 'config.json'); const localConfig = path.resolve(process.cwd(), '.' + pkg.name + '.json'); ```
### Config File Tools [indexzero/nconf](https://github.com/indexzero/nconf) Hierarchical node.js configuration with files, environment variables, command-line arguments, and atomic object merging.
## Packaging & Distribution Make a package! Decide if your package is a module or a script. (or both)
### Registering a bin command ```js // package.json { "name": "foobar", //... "bin": { "foobar": "./src/bin" } // ... ``` * Symlinked into **prefix/bin** for global installs * **./node_modules/.bin/** for local installs.
Make sure that your file(s) referenced in **bin** starts with **#!/usr/bin/env node**, otherwise the scripts are started without the node executable! ```js #!/usr/bin/env node const pkg = require('../../package.json'); ```
### Naming things is hard It's possible to have [zero or more](https://docs.npmjs.com/files/package.json#bin) bin commands ```js "bin": "./bin/cmd.js", // or "bin": { "one": "./bin/one.js", "two": "./bin/two/", } ```
### Remote Diagnostics Allow for introspection [visionmedia/debug](https://github.com/visionmedia/debug#readme) A tiny JavaScript debugging utility modelled after Node.js core's debugging technique. Works in Node.js and web browsers
```js var a = require('debug')('worker:a') , b = require('debug')('worker:b'); (function work() { a('doing lots of uninteresting work'); setTimeout(work, Math.random() * 1000); })(); (function workb() { b('doing some work'); setTimeout(workb, Math.random() * 2000); })(); ``` ![](https://user-images.githubusercontent.com/71256/29091486-fa38524c-7c37-11e7-895f-e7ec8e1039b6.png)
### Remote Logging * Think carefully about whether to send remote logs * Homebrew's Google Analytics tussle
### Communicating Updates Be careful, as this can get annoying ```bash $ nom version [major|minor|patch] # can later be fetched from # https://api.github.com/repos/<user>/<repo>/tags ``` [oclif/plugin-warn-if-update-available](https://github.com/oclif/plugin-warn-if-update-available)
## Ideas
### Automated interactions Propagating CI events * Generating builds * Notifying of events
### Replicating UI Sometimes you don't want to leave the editor/terminal * Remote authoring * Clicking buttons * Consolidated monitoring
### Configure Existing Scripts * What options are you setting with environment variables? * Make those explicit * What options are you editing on the fly? * Make those explicit
## Questions & Thanks [www.andjosh.com/presents](https://www.andjosh.com/presents)