Cliffy

Auto generated help

The help information is auto-generated based on the information you have defined on your commands. The name, version, description, meta information, options, commands, environment variables and examples are displayed in the help.

To display the help you can invoke the help option (-h or --help) or the help command (help) on the main or on one of the sub commands. The help command needs to be registered manually.

To retrieve the help text programmatically you can use the .showHelp() and .getHelp() methods.

import { Command } from "https://deno.land/x/cliffy@v0.25.0/command/command.ts";

await new Command()
  .name("help-option-and-command")
  .version("0.1.0")
  .description("Sample description ...")
  .env(
    "EXAMPLE_ENVIRONMENT_VARIABLE=<value:boolean>",
    "Environment variable description ...",
  )
  .example(
    "Some example",
    "Example content ...\n\nSome more example content ...",
  )
  .parse(Deno.args);Copy
$ deno run https://deno.land/x/cliffy@v0.25.0/examples/command/help.ts --helpCopy

Get help

The .getHelp() method returns the auto generated help as string.

Additional info

You can add some additional information to the help text with the .meta(name, value) method.

new Command()
  .name("example")
  .version("1.0.0")
  .description("Example command.")
  .meta("deno", Deno.version.deno)
  .meta("v8", Deno.version.v8)
  .meta("typescript", Deno.version.typescript)
  .parse();Copy

The additional information is displayed below the command version in the auto generated help.

Usage:   example
  Version: 0.1.0

  deno: 1.16.1
  v8: 9.7.106.2
  typescript: 4.4.2

  Description:

    Example command.Copy

Customize help

The .help() method can be used to disable or enable types, hints and colors for the auto generated help.

import { Command } from "https://deno.land/x/cliffy@v0.25.0/command/command.ts";

await new Command()
  .help({
    // Show argument types.
    types: true, // default: false
    // Show hints.
    hints: true, // default: true
    // Enable/disable colors.
    colors: false, // default: true
  })
  .option("-f, --foo [val:number]", "Some description.", {
    required: true,
    default: 2,
  })
  .parse();Copy

Override help

The .help() method can be also used to override the help output. This overrides the output of the .getHelp() and .showHelp() methods which are used by the help option and help command. The help handler will be also used for all sub command, but can be overridden in each sub command separately.

import { Command } from "https://deno.land/x/cliffy@v0.25.0/command/command.ts";

await new Command()
  .help("My custom help")
  // Can be also a function.
  .help(() => "My custom help")
  .parse();Copy

Help option

The -h and --help option flag prints the auto generated help to stdout.

The short flag -h prints only the first line of each option and command description. With the long flag (--help) the full description is printed for each option and command.

Optionally you can also register the pre-defined help command to display the help.

Customize help option

The help option is completely customizable with the .helpOption() method. It has the same arguments as the normal .option() method. With the first argument you specify the flags followed by the description. The third argument can be an action handler or an options object. The second and third arguments are optional.

await new Command()
  .helpOption("-i, --info", "Print help info.", function (this: Command) {
    console.log("some help info ...", this.getHelp());
  })
  .parse(Deno.args);Copy

You can also override the default options of the help option. The options are the same as for the .option() method.

await new Command()
  .helpOption(" -x, --xhelp", "Print help info.", { global: true })
  .parse(Deno.args);Copy

To disable the help option you can pass false to the .helpOption() method.

await new Command()
  .helpOption(false)
  .parse(Deno.args);Copy

Version option

The --version and -V option flag prints the version number defined with the version() method. The version number will be also display in the auto generated help. If the long --version option is used, the long format will be printed including command name and all meta data defined with the .meta() method.

import { Command } from "https://deno.land/x/cliffy@v0.25.0/command/mod.ts";

await new Command()
  .version("0.1.0")
  .parse(Deno.args);Copy
$ deno run https://deno.land/x/cliffy@v0.25.0/examples/command/version_options.ts -V
$ deno run https://deno.land/x/cliffy@v0.25.0/examples/command/version_options.ts --version
0.0.1Copy

Customize version option

The version option is completely customizable with the .versionOption() method. It has the same arguments as the normal .option() method. With the first argument you specify the flags followed by the description. The third argument can be an action handler or an options object. The second and third arguments are optional.

await new Command()
  .version("0.1.0")
  .versionOption(
    " -x, --xversion",
    "Print version info.",
    function (this: Command) {
      console.log("Version: %s", this.getVersion());
    },
  )
  .parse(Deno.args);Copy

You can also override the default options of the version option. The options are the same as for the .option() method.

await new Command()
  .version("0.1.0")
  .versionOption(" -x, --xversion", "Print version info.", { global: true })
  .parse(Deno.args);Copy

The version option can be also disabled.

await new Command()
  .versionOption(false)
  .parse(Deno.args);Copy

Add examples

You can add some examples for your command which will be displayed in the auto generated help.

import { red } from "https://deno.land/std/fmt/colors.ts";
import { Command } from "https://deno.land/x/cliffy@v0.25.0/command/mod.ts";

await new Command()
  .name("examples")
  .example(
    "example name",
    `Description ...\n\nCan have multiple lines and ${red("colors")}.`,
  )
  .parse(Deno.args);Copy
$ deno run https://deno.land/x/cliffy@v0.25.0/examples/command/examples.ts helpCopy

← Environment variablesShell completions →
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