cmdln

node-cmdln is a node.js helper lib for creating CLI tools with subcommands (think git, svn, zfs, brew, etc.). It is a sister of my earlier Python lib for this.

Follow @trentmick for updates to node-cmdln.

Usage

You define a subclass of Cmdln and subcommands as do_NAME methods. Minimally you could have a "conan.js" as follows:

#!/usr/bin/env node
var util = require('util');
var cmdln = require('cmdln');

function Conan() {
    cmdln.Cmdln.call(this, {
        name: 'conan',
        desc: 'What is best in life?'
    });
}
util.inherits(Conan, cmdln.Cmdln);

Conan.prototype.do_crush = function do_crush(subcmd, opts, args, cb) {
    console.log('Yargh!');
    cb();
};
Conan.prototype.do_crush.help = 'Crush your enemies.';

cmdln.main(new Conan());  // mainline

With this, you get the following behaviour:

$ node examples/conan.js
What is best in life?

Usage:
    conan [OPTIONS] COMMAND [ARGS...]
    conan help COMMAND

Options:
    -h, --help      Show this help message and exit.

Commands:
    help (?)        Help on a specific sub-command.
    crush           Crush your enemies.

$ node examples/conan.js help crush
Crush your enemies.

$ node examples/conan.js crush
Yargh!

Option processing

Option processing (using dashdash) is integrated. do_crush above could be replaced with:

Conan.prototype.do_crush = function (subcmd, opts, args, cb) {
    if (opts.help) {
        this.do_help('help', {}, [subcmd], cb);
        return;
    }
    if (!args.length) {
        console.log('No enemies? Yarg!');
    } else {
        args.forEach(function (enemy) {
            console.log('Smite %s with a %s!', enemy, opts.weapon);
        });
    }
    cb();
};
Conan.prototype.do_crush.options = [
    {
        names: ['help', 'h'],
        type: 'bool',
        help: 'Show this help.'
    },
    {
        names: ['weapon', 'w'],
        helpArg: 'WEAPON',
        type: 'string',
        default: 'sword',
        help: 'Weapon with which to smite.'
    }
];
Conan.prototype.do_crush.help = (
    'Crush your enemies.\n'
    + '\n'
    + 'Usage:\n'
    + '     {{name}} {{cmd}} [OPTIONS] [ENEMIES...]\n'
    + '\n'
    + '{{options}}'
);

Then we get this behaviour:

$ node examples/conan.js crush Bob
Smite Bob with a sword!

$ node examples/conan.js crush Bob Linda --weapon mattock
Smite Bob with a mattock!
Smite Linda with a mattock!

$ node examples/conan.js crush -h
Crush your enemies.

Usage:
     conan crush [OPTIONS] [ENEMIES...]

Options:
    -h, --help                  Show this help.
    -w WEAPON, --weapon=WEAPON  Weapon with which to smite.

See examples/conan.js for the complete example. Run node example/conan.js ... to try it out.

Bash completion

One can generate Bash completion code for a Cmdln subclass via

cli.bashCompletion()

One possible usage is to add a completion subcmd to your CLI:

CLI.prototype.do_completion = function (subcmd, opts, args, cb) {
    console.log( this.bashCompletion() );
    cb();
};

and get users to use that to setup Bash completion:

$ alias conan="node examples/conan.js"
$ conan completion > conan.completion
$ source conan.completion
$ conan <TAB>
--help      --version   -v          completion  hear        see
--verbose   -h          -x          crush       help        smash

Another potential usage could be to pre-generate a completion file for, and distribute it with, your tool.

Reference

In general, please read the comments in the source and browse the examples. The API is far from fully documented here.

cmdln.Cmdln

To use this module you create a class that inherits from cmdln.Cmdln; add some methods to that class that define the tool's commands, options, etc.; then pass an instance to cmdln.main(). Roughly like this:

function CLI() {
    cmdln.Cmdln.call(this, {<config>});
}
util.inherits(CLI, cmdln.Cmdln);
...
var cli = new CLI();
cmdln.main(cli);

We'll use the CLI and cli names as used above in the following reference:

• new Cmdln(<config>) Create a Cmdln subclass instance. See the block comment in the code for full documentation on the config options.

• CLI.prototype.do_<subcmd> = function (subcmd, opts, args, cb) is how a subcommand is defined. How the subcmd is handled can be customize with some properties (e.g. options, help) on the handler function.

• CLI.prototype.do_<subcmd> = <SubCLI>; Instead of a function handler for a subcommand, a do_<subcmd> can be set to another Cmdln subclass to support sub-subcommands, like git remote add|remove|rename|.... See "examples/fauxgit.js" for an example.

• CLI.prototype.do_<subcmd>.aliases = <array of strings>; to define one or more aliases for a command. These aliases are shown in the "Commands:" section of the generated help output.

• CLI.prototype.do_<subcmd>.hiddenAliases = <array of strings>; to define one or more aliases for a command that are not shown in the generated help output. This can be useful when renaming a subcommand in a new version of a tool and still support the old name.

• CLI.prototype.do_<subcmd>.options = <object>; is how to set the options (in dashdash format) for that subcommand.

• CLI.prototype.do_<subcmd>.helpOpts = <dashdash helpOpts object>; to override formatting settings for options help output for this command. By default the helpOpts passed into the CLI constructor are used. The set of supported helpOpts are defined by dashdash.

• CLI.prototype.do_<subcmd>.help = <string>; to set the help string for a subcommand. This supports some template variables:

  • {{name}} becomes cli.name (i.e. the tool name).
  • {{cmd}} becomes the sub-command name.

• CLI.prototype.do_<subcmd>.help = function (subcmd, opts, args, cb) is an alternate method to handle help for a subcommand. The given function will be run when tool help <subcmd> is called.

• CLI.prototype.do_<subcmd>.desc = <string>; can be set to a short string to be used in the tool help output to summarize subcmd. If not provided, then the first line of do_<subcmd>.help will be used.

• CLI.prototype.do_<subcmd>.hidden = <boolean>; Set to false to have tool help output not list this subcmd.

• CLI.prototype.do_<subcmd>.interspersedOptions = <boolean>; Set to false to have tool <subcmd> ... not allow interspersed options (i.e. options after the first argument).

• CLI.prototype.do_<subcmd>.allowUnknownOptions = <boolean>; Set to true to have tool <subcmd> ... allow unknown options.

• CLI.prototype.init(opts, args, cb) Hook run after option processing (this.opts is set), but before the subcommand handler is run.

• CLI.prototype.fini(subcmd, err, cb) Hook run after the subcommand handler is run. Here err is the error returned by the invocation of the CLI. This allows a fini method to use or deal with that error, if necessary. To just pass that err on (to the calling main) do this:

    CLI.prototype.fini = function fini(subcmd, err, cb) {
        // Whatever finalization you want to do here (possibly with a
        // `finiErr`) ...
        cb(finiErr || err, subcmd);
    };
  

  (Note: The call signature to fini changed in cmdln v3. See the changelog in CHANGES.md.)

• [Backward incompatible change] Change the signature of a <cmdln>.fini method from:

    MyCLI.prototype.fini = function fini(subcmd, cb) {
  

  to:

    MyCLI.prototype.fini = function fini(subcmd, err, cb) {
  

  where err is the error returned by the invocation of the CLI. This allows a fini method to use or deal with that error, if necessary.

• cli.showErrStack boolean. Set to true to have cmdln.main(), if used, print a full stack on a shown error. When wanted, this is typically set in If you want this option it is typically set either

• cli.handlerFromSubcmd(<subcmd>) will return the appropriate do_<subcmd> method that handles the given sub-command. This resolves sub-command aliases.

• cli.helpFromSubcmd(<subcmd>) will return the help string for that subcmd or, if defined, the help function defined for that subcmd. This is used by the default do_help implementation.

• cli.bashCompletion() generates and returns bash completion for the CLI.

cmdln.main()

This is a convenience method for driving the mainline of your script using the your defined Cmdln subclass. There are a number of options to control how it works. Read the block comment on that function in "lib/cmdln.js" for the best docs.

License

MIT. See LICENSE.txt

Changelog

3.4.1

• Fix a bug in Cmdln.prototype.main where it could callback twice if there was an OptionError processing the top-level options. This wasn't noticed because the commonly used cmdln.main() function that calls it would process.exit on the first callback.