Commander.js


The complete solution for node.js command-line interfaces, inspired by Ruby's commander.

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- Commander.js
- Installation
- Declaring _program_ variable
- Options
- Common option types, boolean and value
- Default option value
- Other option types, negatable boolean and flag|value
- Custom option processing
- Required option
- Version option
- Commands
- Specify the argument syntax
- Action handler (sub)commands
- Stand-alone executable (sub)commands
- Automated help
- Custom help
- .usage and .name
- .help(cb)
- .outputHelp(cb)
- .helpInformation()
- .helpOption(flags, description)
- .addHelpCommand()
- Custom event listeners
- Bits and pieces
- .parse() and .parseAsync()
- Avoiding option name clashes
- TypeScript
- createCommand()
- Node options such as --harmony
- Debugging stand-alone executable subcommands
- Override exit handling
- Examples
- License
- Support
- Commander for enterprise

Installation

``bash
npm install commander
`

Declaring _program_ variable

Commander exports a global object which is convenient for quick programs.
This is used in the examples in this README for brevity.

`js
const { program } = require('commander');
program.version('0.0.1');
`

For larger programs which may use commander in multiple ways, including unit testing, it is better to create a local Command object to use.

`js
const { Command } = require('commander');
const program = new Command();
program.version('0.0.1');
`

Options

Options are defined with the .option() method, also serving as documentation for the options. Each option can have a short flag (single character) and a long name, separated by a comma or space or vertical bar ('|').

The options can be accessed as properties on the Command object. Multi-word options such as "--template-engine" are camel-cased, becoming program.templateEngine etc. See also optional new behaviour to avoid name clashes.

Multiple short flags may optionally be combined in a single argument following the dash: boolean flags, the last flag may take a value, and the value.
For example -a -b -p 80 may be written as -ab -p80 or even -abp80.

You can use -- to indicate the end of the options, and any remaining arguments will be used without being interpreted.
This is particularly useful for passing options through to another
command, like: do -- git --version.

Options on the command line are not positional, and can be specified before or after other command arguments.

$3

The two most used option types are a boolean flag, and an option which takes a value (declared using angle brackets). Both are undefined unless specified on command line.

`js
const { program } = require('commander');

program
.option('-d, --debug', 'output extra debugging')
.option('-s, --small', 'small pizza size')
.option('-p, --pizza-type ', 'flavour of pizza');

program.parse(process.argv);

if (program.debug) console.log(program.opts());
console.log('pizza details:');
if (program.small) console.log('- small pizza size');
if (program.pizzaType) console.log(- ${program.pizzaType});
`

`bash
$ pizza-options -d
{ debug: true, small: undefined, pizzaType: undefined }
pizza details:
$ pizza-options -p
error: option '-p, --pizza-type ' argument missing
$ pizza-options -ds -p vegetarian
{ debug: true, small: true, pizzaType: 'vegetarian' }
pizza details:
- small pizza size
- vegetarian
$ pizza-options --pizza-type=cheese
pizza details:
- cheese
`

program.parse(arguments) processes the arguments, leaving any args not consumed by the program options in the program.args array.

$3

You can specify a default value for an option which takes a value.

`js
const { program } = require('commander');

program
.option('-c, --cheese ', 'add the specified type of cheese', 'blue');

program.parse(process.argv);

console.log(cheese: ${program.cheese});
`

`bash
$ pizza-options
cheese: blue
$ pizza-options --cheese stilton
cheese: stilton
`

$3

You can specify a boolean option long name with a leading no- to set the option value to false when used.
Defined alone this also makes the option true by default.

If you define --foo first, adding --no-foo does not change the default value from what it would
otherwise be. You can specify a default boolean value for a boolean flag and it can be overridden on command line.

`js
const { program } = require('commander');

program
.option('--no-sauce', 'Remove sauce')
.option('--cheese ', 'cheese flavour', 'mozzarella')
.option('--no-cheese', 'plain with no cheese')
.parse(process.argv);

const sauceStr = program.sauce ? 'sauce' : 'no sauce';
const cheeseStr = (program.cheese === false) ? 'no cheese' : ${program.cheese} cheese;
console.log(You ordered a pizza with ${sauceStr} and ${cheeseStr});
`

`bash
$ pizza-options
You ordered a pizza with sauce and mozzarella cheese
$ pizza-options --sauce
error: unknown option '--sauce'
$ pizza-options --cheese=blue
You ordered a pizza with sauce and blue cheese
$ pizza-options --no-sauce --no-cheese
You ordered a pizza with no sauce and no cheese
`

You can specify an option which functions as a flag but may also take a value (declared using square brackets).

`js
const { program } = require('commander');

program
.option('-c, --cheese [type]', 'Add cheese with optional type');

program.parse(process.argv);

if (program.cheese === undefined) console.log('no cheese');
else if (program.cheese === true) console.log('add cheese');
else console.log(add cheese type ${program.cheese});
`

`bash
$ pizza-options
no cheese
$ pizza-options --cheese
add cheese
$ pizza-options --cheese mozzarella
add cheese type mozzarella
`

$3

You may specify a function to do custom processing of option values. The callback function receives two parameters, the user specified value and the
previous value for the option. It returns the new value for the option.

This allows you to coerce the option value to the desired type, or accumulate values, or do entirely custom processing.

You can optionally specify the default/starting value for the option after the function.

`js
const { program } = require('commander');

function myParseInt(value, dummyPrevious) {
// parseInt takes a string and an optional radix
return parseInt(value);
}

function increaseVerbosity(dummyValue, previous) {
return previous + 1;
}

function collect(value, previous) {
return previous.concat([value]);
}

function commaSeparatedList(value, dummyPrevious) {
return value.split(',');
}

program
.option('-f, --float ', 'float argument', parseFloat)
.option('-i, --integer ', 'integer argument', myParseInt)
.option('-v, --verbose', 'verbosity that can be increased', increaseVerbosity, 0)
.option('-c, --collect ', 'repeatable value', collect, [])
.option('-l, --list ', 'comma separated list', commaSeparatedList)
;

program.parse(process.argv);

if (program.float !== undefined) console.log(float: ${program.float});
if (program.integer !== undefined) console.log(integer: ${program.integer});
if (program.verbose > 0) console.log(verbosity: ${program.verbose});
if (program.collect.length > 0) console.log(program.collect);
if (program.list !== undefined) console.log(program.list);
`

`bash
$ custom -f 1e2
float: 100
$ custom --integer 2
integer: 2
$ custom -v -v -v
verbose: 3
$ custom -c a -c b -c c
[ 'a', 'b', 'c' ]
$ custom --list x,y,z
[ 'x', 'y', 'z' ]
`

$3

You may specify a required (mandatory) option using .requiredOption. The option must have a value after parsing, usually specified on the command line, or perhaps from a default value (say from environment). The method is otherwise the same as .option in format, taking flags and description, and optional default value or custom processing.

`js
const { program } = require('commander');

program
.requiredOption('-c, --cheese ', 'pizza must have cheese');

program.parse(process.argv);
`

`bash
$ pizza
error: required option '-c, --cheese ' not specified
`

$3

The optional version method adds handling for displaying the command version. The default option flags are -V and --version, and when present the command prints the version number and exits.

`js
program.version('0.0.1');
`

`bash
$ ./examples/pizza -V
0.0.1
`

You may change the flags and description by passing additional parameters to the version method, using
the same syntax for flags as the option method. The version flags can be named anything, but a long name is required.

`js
program.version('0.0.1', '-v, --vers', 'output the current version');
`

Commands

You can specify (sub)commands for your top-level command using .command() or .addCommand(). There are two ways these can be implemented: using an action handler attached to the command, or as a stand-alone executable file (described in more detail later). The subcommands may be nested (example).

In the first parameter to .command() you specify the command name and any command arguments. The arguments may be or [optional], and the last argument may also be variadic....

You can use .addCommand() to add an already configured subcommand to the program.

For example:

`js
// Command implemented using action handler (description is supplied separately to .command)
// Returns new command for configuring.
program
.command('clone [destination]')
.description('clone a repository into a newly created directory')
.action((source, destination) => {
console.log('clone command called');
});

// Command implemented using stand-alone executable file (description is second parameter to .command)
// Returns top-level command for adding more commands.
program
.command('start ', 'start named service')
.command('stop [service]', 'stop named service, or all if no name supplied');

// Command prepared separately.
// Returns top-level command for adding more commands.
program
.addCommand(build.makeBuildCommand());
`

Configuration options can be passed with the call to .command(). Specifying true for opts.noHelp will remove the command from the generated help output. Specifying true for opts.isDefault will run the subcommand if no other subcommand is specified (example).

$3

You use .arguments to specify the arguments for the top-level command, and for subcommands they are included in the .command call. Angled brackets (e.g. ) indicate required input. Square brackets (e.g. [optional]) indicate optional input.

`js
const { program } = require('commander');

program
.version('0.1.0')
.arguments(' [env]')
.action(function (cmd, env) {
cmdValue = cmd;
envValue = env;
});

program.parse(process.argv);

if (typeof cmdValue === 'undefined') {
console.error('no command given!');
process.exit(1);
}
console.log('command:', cmdValue);
console.log('environment:', envValue || "no environment given");
`

The last argument of a command can be variadic, and only the last argument. To make an argument variadic you
append ... to the argument name. For example:

`js
const { program } = require('commander');

program
.version('0.1.0')
.command('rmdir