Command Flags

Flag options are non-positional arguments passed to the command. Flags can either be option flags which take an argument, or boolean flags which do not. An option flag must have an argument.

For example, if this command was run like this:

$ mycli --force --file=./myfile

It would be declared like this:

import {Command, Flags} from '@oclif/core'

export class MyCLI extends Command {
  static flags = {
    // can pass either --force or -f
    force: Flags.boolean({char: 'f'}),
    file: Flags.string(),
  }

  async run() {
    const {flags} = await this.parse(MyCLI)
    if (flags.force) console.log('--force is set')
    if (flags.file) console.log(`--file is: ${flags.file}`)
  }
}

oclif supports a wide range of alternative flag inputs.

Here are the options flags can have:

static flags = {
  name: Flags.string({
    // The following can be set on both boolean and option flag (e.g. string, integer, url, custom, etc) types.
    char: 'n',                                   // shorter flag version
    summary: 'brief summary',                    // help summary for flag
    helpLabel: '--my-flags',                     // The flag label to show in help. Defaults to "[-<char>] --<name>" where -<char> is only displayed if the char is defined.
    helpGroup: 'THE BEST FLAGS',                 // Put flag into THE BEST FLAGS group in help
    description: 'in-depth overview',            // help description for flag
    hidden: false,                               // hide from help
    multiple: false,                             // allow setting this flag multiple times
    env: 'MY_NAME',                              // default to value of environment variable
    options: ['a', 'b'],                         // only allow the value to be from a discrete set
    parse: async input => 'output',              // instead of the user input, return a different value
    default: 'world',                            // default value if flag not passed (can be an async function that returns a string or undefined)
    defaultHelp: 'a dynamic value'               // dynamic default value to show in help output (e.g. current working directory). Can be an async function that returns a string or undefined
    required: false,                             // make flag required
    aliases: ['username', 'u'],                  // aliases for the flag - can be short char or long flags
    aliases: ['u', 'n'],                         // single character aliases for the flag
    deprecated: false,                           // mark the flag as deprecated.
    deprecateAliases: false,                     // emit deprecation warning anytime a flag alias is provided
    noCacheDefault: false,                       // if true, the value returned by defaultHelp will not be cached in the oclif.manifest.json.
    dependsOn: ['extra-flag'],                   // this flag requires another flag
    exclusive: ['extra-flag'],                   // this flag cannot be specified alongside this other flag
    exactlyOne: ['extra-flag', 'another-flag'],  // exactly one of these flags must be provided
    relationships: [                             // define complex relationships between flags
      // Make this flag dependent on all of these flags
      {type: 'all', flags: ['flag-one', 'flag-two']}
      // Make this flag dependent on at least one of these flags
      {type: 'some', flags: ['flag-three', 'flag-four']}
      // Make this flag exclusive of all these flags
      {type: 'none', flags: ['flag-five', 'flag-six']}

      // Make this flag dependent on all of these flags
      {type: 'all', flags: [
        'flag-one',
        'flag-two',
        // Include flag-seven but only when flag-eight is equal to FooBar
        {name: 'flag-seven', when: async (flags) => flags['flag-eight'] === 'FooBar'}
      ]}
    ],
    // The following properties cannot be set on boolean flags
    helpValue: '<name>',                         // The flag value to show in help. Defaults to "<value>",
    multipleNonGreedy: false,                    // Parse one value per flag to allow `-m val1 -m val2` but disallow `-m val1 val2`. Only respected if multiple is set to true
    delimiter: ','                               // Delimiter to separate the values for a multiple value flag. Only respected if multiple is set to true. Default behavior is to separate on spaces.
    allowStdin: false,                           // Allow input value to be read from stdin if the provided value is `-`. Can also be set to `only` to allow flag to always read from stdin even if no value is provided.
  }),

  // flag with no value (-f, --force)
  force: Flags.boolean({
    // Boolean flags take all the same properties described in the previous example
    // in addition to:
    allowNo: true // Support reversible boolean flag with `--no-` prefix (e.g. `--no-force`). This is disabled by default.
  }),
}

Custom Flags

For larger CLIs, it can be useful to declare a custom flag that can be shared amongst multiple commands. Here is an example of a custom flag:

// src/flags.ts
import {Flags} from '@oclif/core'

class Team {
  public name: string;
  // etc...
}

function getTeam(): Promise<Team> {
  // imagine this reads a configuration file or something to find the team
  return new Team()
}

export const team = Flags.custom<Team>({
  char: 't',
  description: 'team to use',
  default: async () => getTeam(),
})

// src/commands/mycommand.ts
import {team} from '../flags'
import {Command} from '@oclif/core'

export class MyCLI extends Command {
  static flags = {
    team: team({
      required: true,
    }),
  }

  async run() {
    const {flags} = await this.parse(MyCLI)
    if (flags.team) console.log(`--team is ${flags.team.name}`)
  }
}

In the Salesforce CLI we make heavy use of custom flags. For example,

• A salesforceId flag that ensures the provided string is a valid Salesforce Id.
• A duration flag that converts a provided integer into a Duration instance that we use for working with time based values.

These and more are located here if you want to see more examples. You can also read the API docs.

Alternative Flag Inputs

Here are some other ways the user can use input flags. This is assuming the command has flags like -f, --file=file and -v, --verbose (string and boolean flag):

$ mycli --verbose
$ mycli -v
$ mycli --file=foo
$ mycli --file foo
$ mycli -f foo
$ mycli -f=foo
$ mycli -ffoo
$ mycli -vffoo

The last one seems a little odd at first glance, but it's relatively standard in unix and makes commands like tar -xvzfmytarball.tar.gz possible.

See our blog post CLI Flags Explained for a deeper dive into CLI flags.