Docs
Start Building for Free
CircleCI.comAcademyBlogCommunitySupport

Reusable Config Reference Guide

yesterday12 min read
Cloud
Server v4.x
Server v3.x
On This Page

This guide describes how to get started with reusable commands, jobs, executors and orbs. This guide also covers the use of parameters for creating parameterized reusable elements.

Notes on reusable configuration

  • Install the CircleCI CLI so that you have access to the circleci config process command (optional). This command lets you see the expanded configuration with all reusable keys processed. Follow the Using the CircleCI CLI documentation for installation instructions and tips.

  • CircleCI reusable configuration elements require a version: 2.1 .circleci/config.yml file.

  • Command, job, executor, and parameter names must start with a letter and can only contain lowercase letters (a-z), digits (0-9), underscores (_) and hyphens (-).

Using the parameters declaration

Parameters are declared by name under a job, command, or executor. Pipeline parameters are defined at the top level of a project configuration. See the Pipeline Values and Parameters guide for more information.

The immediate children of the parameters key are a set of keys in a map.

In the following example, a command named greeting is designed with a single parameter named to. The to parameter is used within the steps to echo Hello back to the user.

version: 2.1
commands: # a reusable command with parameters
  greeting:
    parameters:
      to:
        default: "world"
        type: string
    steps:
      - run: echo "Hello <<parameters.to>>"
jobs:
  my-job:
    docker:
      - image: cimg/base:stable
    steps:
      - greeting:
          to: "My-Name"
workflows:
  my-workflow:
    jobs:
      - my-job

Parameter syntax

A parameter can have the following keys as immediate children:

Key NameDescriptionDefault value
descriptionOptional. Used to generate documentation for your orb.N/A
typeRequired. See Parameter Types in the section below for details.N/A
defaultThe default value for the parameter. Required for pipeline parameters. For all other parameters, if not present, the parameter is implied to be required.N/A

Parameter types

This section describes the types of parameters and their usage.

The parameter types supported by orbs are:

  • string
  • boolean
  • integer
  • enum
  • executor
  • steps
  • environment variable name

The parameter types supported by pipeline parameters are:

  • string
  • boolean
  • integer
  • enum

String

Basic string parameters are described below:

version: 2.1
commands:
  copy-markdown:
    parameters:
      destination:
        description: destination directory
        type: string
        default: docs
    steps:
      - run: cp *.md << parameters.destination >>

Strings must be enclosed in quotes if they would otherwise represent another type (such as boolean or number) or if they contain characters that have special meaning in YAML, particularly for the colon character. In all other instances, quotes are optional.

Empty strings are treated as a falsy value in evaluation of when clauses, and all other strings are treated as truthy. Using an unquoted string value that YAML interprets as a boolean will result in a type error.

Boolean

Boolean parameters are useful for conditionals:

version: 2.1
commands:
  npm-install:
    parameters:
      clean:
        description: Perform a clean install
        type: boolean
        default: false
    steps:
      - when:
          condition: << parameters.clean >>
          steps:
            - run: npm clean-install
      - when:
          condition:
            not: << parameters.clean >>
          steps:
            - run: npm install

Boolean parameter evaluation is based on the values specified in YAML 1.1:

  • True: y yes true on
  • False: n no false off

Capitalized and uppercase versions of the above values are also valid.

Integer

Use the parameter type integer to pass a numeric integer value.

The following example uses the integer type to populate the value of parallelism in a job:

version: 2.1
jobs:
  build:
    parameters:
      p:
        type: integer
        default: 1
    parallelism: << parameters.p >>
    docker:
      - image: cimg/base:2023.11
    steps:
      - checkout
workflows:
  workflow:
    jobs:
      - build:
          p: 2

Enum

The enum parameter may be a list of any values. Use the enum parameter type when you want to enforce that the value must be one from a specific set of string values.

The following example uses the enum parameter to declare the target operating system for a binary:

version: 2.1

commands:
  list-files:
    parameters:
      os:
        default: "linux"
        description: The target Operating System for the heroku binary. Must be one of "linux", "darwin", "win32".
        type: enum
        enum: ["linux", "darwin", "win32"]

The following enum type declaration is invalid because the default is not declared in the enum list.

version: 2.1

commands:
  list-files:
    parameters:
      os:
        type: enum
        default: "windows" #invalid declaration of default that does not appear in the comma-separated enum list
        enum: ["darwin", "linux"]

Executor

Use an executor parameter type to allow the invoker of a job to decide what executor it will run on.

version: 2.1

executors:
  xenial:
    parameters:
      some-value:
        type: string
        default: foo
    environment:
      SOME_VAR: << parameters.some-value >>
    docker:
      - image: ubuntu:xenial
  bionic:
    docker:
      - image: ubuntu:bionic

jobs:
  test:
    parameters:
      e:
        type: executor
    executor: << parameters.e >>
    steps:
      - run: some-tests

workflows:
  workflow:
    jobs:
      - test:
          e: bionic
      - test:
          e:
            name: xenial
            some-value: foobar

Steps

Steps are used when you have a job or command that needs to mix predefined and user-defined steps. When passed in to a command or job invocation, the steps passed as parameters are always defined as a sequence, even if only one step is provided.

version: 2.1

commands:
  run-tests:
    parameters:
      after-deps:
        description: "Steps that will be executed after dependencies are installed, but before tests are run"
        type: steps
        default: []
    steps:
      - run: make deps
      - steps: << parameters.after-deps >>
      - run: make test

The following example demonstrates that steps passed as parameters are given as the value of a steps declaration under the job’s steps.

version: 2.1

commands:
  run-tests:
    parameters:
      after-deps:
        description: "Steps that will be executed after dependencies are installed, but before tests are run"
        type: steps
        default: []
    steps:
      - run: make deps
      - steps: << parameters.after-deps >>
      - run: make test

jobs:
  build:
    docker:
      - image: cimg/base:2023.11
    steps:
      - run-tests:
          after-deps:
            - run: echo "The dependencies are installed"
            - run: echo "And now I'm going to run the tests"

The above will resolve to the following:

version: 2.1
steps:
  - run: make deps
  - run: echo "The dependencies are installed"
  - run: echo "And now I'm going to run the tests"
  - run: make test

Environment variable name

The environment variable name (env_var_name) parameter is a string that must match a POSIX_NAME regular expression (for example, there can be no spaces or special characters). The env_var_name parameter is a more meaningful parameter type that enables CircleCI to check that the string that has been passed can be used as an environment variable name. For more information on environment variables, see the guide to Environment Variables.

The example below shows you how to use the env_var_name parameter type for deploying to AWS S3 with a reusable build job. This example uses the AWS_ACCESS_KEY and AWS_SECRET_KEY environment variables with the access-key and secret-key parameters. If you have a deploy job that runs the s3cmd, it is possible to create a reusable command that uses the needed authentication, but deploys to a custom bucket.

Original config.yml file:

version: 2.1

jobs:
  build:
    docker:
    - image: ubuntu:latest
    steps:
    - run:
        command: |
          s3cmd --access_key ${FOO_BAR} \
                --secret_key ${BIN_BAZ} \
                ls s3://some/where
workflows:
  workflow:
    jobs:
    - build

New config.yml file:

version: 2.1

jobs:
   build:
     parameters:
       access-key:
         type: env_var_name
         default: AWS_ACCESS_KEY
       secret-key:
         type: env_var_name
         default: AWS_SECRET_KEY
       command:
         type: string
     docker:
       - image: ubuntu:latest
     steps:
       - run: |
           s3cmd --access_key ${<< parameters.access-key >>} \\
                 --secret_key ${<< parameters.secret-key >>} \\
                 << parameters.command >>
workflows:
  workflow:
    jobs:
      - build:
          access-key: FOO_BAR
          secret-key: BIN_BAZ
          command: ls s3://some/where

Authoring reusable commands

Commands are declared under the commands key of a .circleci/config.yml file. The following example defines a command called sayhello, which accepts a string parameter to:

version: 2.1

commands:
  sayhello:
    description: "A very simple command for demonstration purposes"
    parameters:
      to:
        type: string
        default: "World"
    steps:
      - run: echo Hello << parameters.to >>

The commands key

A command defines a sequence of steps as a map to be executed in a job, enabling you to reuse a single command definition across multiple jobs.

KeyRequiredTypeDescription
stepsYSequenceA sequence of steps that run inside the job that calls the command.
parametersNMapA map of parameter keys. See the Parameter Syntax section for details.
descriptionNStringA string that describes the purpose of the command. Used for generating documentation.

Invoking reusable commands

Reusable commands are invoked with specific parameters as steps inside a job. When using a command, the steps of that command are inserted at the location where the command is invoked. Commands may only be used as part of the sequence under steps in a job.

The following example uses the same command from the previous example – sayhello – and invokes it in the job myjob, passing it a value for the to parameter:

version: 2.1

commands:
  sayhello:
    description: "A very simple command for demonstration purposes"
    parameters:
      to:
        type: string
        default: "World"
    steps:
      - run: echo Hello << parameters.to >>

jobs:
  myjob:
    docker:
      - image: "cimg/base:stable"
    steps:
      - sayhello: # invoke command "sayhello"
          to: "Lev"

Invoking other commands in a command

Commands can use other commands in the scope of execution. For instance, if a command is declared inside an orb it can use other commands in that orb. It can also use commands defined in other orbs that you have imported (for example some-orb/some-command).

Special keys

CircleCI has several special keys available to all circleci.com customers and available by default in CircleCI server installations. Examples of these keys are:

  • checkout
  • setup_remote_docker
  • persist_to_workspace

Commands usage examples

The following is an example of part of the aws-s3 orb where a command called sync is defined:

#...
sync:
    description: Syncs directories and S3 prefixes.
    parameters:
        arguments:
            default: ""
            description: |
                Optional additional arguments to pass to the `aws sync` command (e.g., `--acl public-read`). Note: if passing a multi-line value to this parameter, include `\` characters after each line, so the Bash shell can correctly interpret the entire command.
            type: string
        aws-access-key-id:
            default: AWS_ACCESS_KEY_ID
            description: aws access key id override
            type: env_var_name
        aws-region:
            default: AWS_REGION
            description: aws region override
            type: env_var_name
        aws-secret-access-key:
            default: AWS_SECRET_ACCESS_KEY
            description: aws secret access key override
            type: env_var_name
        from:
            description: A local *directory* path to sync with S3
            type: string
        to:
            description: A URI to an S3 bucket, i.e. 's3://the-name-my-bucket'
            type: string
    steps:
        - aws-cli/setup:
            aws-access-key-id: << parameters.aws-access-key-id >>
            aws-region: << parameters.aws-region >>
            aws-secret-access-key: << parameters.aws-secret-access-key >>
        - deploy:
            command: |
                aws s3 sync \
                  <<parameters.from>> <<parameters.to>> <<parameters.arguments>>
            name: S3 Sync
#...

To invoke this sync command in your 2.1 .circleci/config.yml file, see the following example:

version: 2.1

orbs:
  aws-s3: circleci/aws-s3@4.1.0

jobs:
  deploy2s3:
    docker:
      - image: cimg/base:2023.06
    steps:
      - aws-s3/sync:
          from: .
          to: "s3://mybucket_uri"

workflows:
  build-test-deploy:
    jobs:
      - deploy2s3

Defining a build job:

version: 2.1

orbs:
  aws-cli: circleci/aws-cli@5.1.1
  aws-s3: circleci/aws-s3@4.1.0

jobs:
  build:
    executor: aws-cli/default
    steps:
      - checkout
      - run: mkdir bucket && echo "lorum ipsum" > bucket/build_asset.txt
      - aws-s3/sync:
          from: bucket
          to: "s3://my-s3-bucket-name/prefix"
      - aws-s3/copy:
          from: bucket/build_asset.txt
          to: "s3://my-s3-bucket-name"
          arguments: --dryrun

Authoring reusable executors

Executors define the environment in which the steps of a job will be run. When declaring a job in CircleCI configuration, you define the type of execution environment (docker, machine, macos. etc.) to run in, as well as any other parameters for that environment, including: environment variables to populate, which shell to use, what size resource_class to use, etc.

Executor declarations outside of jobs can be used by all jobs in the scope of that declaration, allowing you to reuse a single executor definition across multiple jobs.

An executor definition includes one or more of the following keys:

  • docker or machine or macos
  • environment
  • working_directory
  • shell
  • resource_class

In the following example my-executor is used for running the job my-job.

version: 2.1
executors:
  my-executor:
    docker:
      - image: cimg/ruby:2.5.1-browsers
jobs:
  my-job:
    executor: my-executor
    steps:
      - run: echo outside the executor

The executors key

Executors define the environment in which the steps of a job will be run, allowing you to reuse a single executor definition across multiple jobs.

KeyRequiredTypeDescription
dockerY (1)ListOptions for docker executor.
resource_classNStringAmount of CPU and RAM allocated to each container in a job.
machineY (1)MapOptions for machine executor.
macosY (1)MapOptions for macOS executor.
shellNStringShell to use for execution command in all steps. Can be overridden by shell in each step.
working_directoryNStringThe directory in which to run the steps.
environmentNMapA map of environment variable names and values.

Example:

version: 2.1
executors:
  my-executor:
    docker:
      - image: cimg/ruby:2.5.1-browsers
jobs:
  my-job:
    executor: my-executor
    steps:
      - run: echo outside the executor

Invoking reusable executors

The following example passes my-executor as the value of a name key under executor – this method is primarily employed when passing parameters to executor invocations:

version: 2.1

executors:
  my-executor:
    docker:
      - image: cimg/ruby:3.2.2
jobs:
  my-job:
    executor:
      name: my-executor
    steps:
      - run: echo outside the executor

It is also possible to allow an orb to define the executor used by all of its commands. This allows users to execute the commands of that orb in the execution environment defined by the orb’s author.

Example of using an executor declared in config.yml with matrix jobs.

The following example declares a Docker executor with a node image, node-docker. The tag portion of the image string is parameterized with a version parameter. A version parameter is also included in the test job so that it can be passed through the job into the executor when the job is called from a workflow.

When calling the test job in the matrix-tests workflow, matrix jobs are used to run the job multiple times, concurrently, each with a different set of parameters. The Node application is tested against many versions of Node.js:

version: 2.1

executors:
  node-docker: # declares a reusable executor
    parameters:
      version:
        description: "version tag"
        default: "lts"
        type: string
    docker:
      - image: cimg/node:<<parameters.version>>

jobs:
  test:
    parameters:
      version:
        description: "version tag"
        default: "lts"
        type: string
    executor:
      name: node-docker
      version: <<parameters.version>>
    steps:
      - checkout
      - run: echo "how are ya?"

workflows:
  matrix-tests:
    jobs:
      - test:
          matrix:
            parameters:
              version:
                - 13.11.0
                - 12.16.0
                - 10.19.0

Using executors defined in an orb

You can also refer to executors from other orbs. Users of an orb can invoke its executors. For example, foo-orb could define the bar executor:

version: 2.1
# Yaml from foo-orb
executors:
  bar:
    docker:
      - image: cimg/base:2023.11
    environment:
      RUN_TESTS: foobar

baz-orb could define the bar executor too:

version: 2.1
# Yaml from baz-orb
executors:
  bar:
    docker:
      - image: cimg/base:stable

You may use either executor from your configuration file with:

version: 2.1
# config.yml
orbs:
  foo-orb: somenamespace/foo@1
  baz-orb: someothernamespace/baz@3.3.1
jobs:
  some-job:
    executor: foo-orb/bar  # prefixed executor
  some-other-job:
    executor: baz-orb/bar  # prefixed executor

Note: The foo-orb/bar and baz-orb/bar are different executors. They both have the local name bar relative to their orbs, but they are independent executors defined in different orbs.

Overriding keys when invoking an executor

When invoking an executor in a job, any keys in the job itself will override those of the executor invoked. For example, if your job declares a docker stanza, it will be used, in its entirety, instead of the one in your executor.

version: 2.1

executors:
  node:
    docker:
      - image: cimg/node:lts
    environment:
      ENV: ci

jobs:
  build:
    docker:
      - image: cimg/base:stable
    # The test executor below will be overwritten by the more explicit "docker" executor. Any env vars will be added.
    executor: node
    steps:
      - run: echo "Node will not be installed."

The above config would resolve to the following:

version: 2.1
jobs:
  build:
    docker:
      - image: cimg/base:stable
    environment:
      ENV: ci       # From executor.
    steps:
      - run: echo "Node will not be installed."

Authoring parameterized jobs

It is possible to invoke the same job more than once in the workflows stanza of .circleci/config.yml, passing any necessary parameters as subkeys to the job. See the Parameters syntax section above for details of syntax usage.

Example of defining and invoking a parameterized job in a config.yml:

version: 2.1

jobs:
  sayhello: # defines a parameterized job
    description: A job that does very little other than demonstrate what a parameterized job looks like
    parameters:
      saywhat:
        description: "To whom shall we say hello?"
        default: "World"
        type: string
    docker:
      - image: cimg/base:2023.11
    steps:
      - run: echo "Hello << parameters.saywhat >>"

workflows:
  build:
    jobs:
      - sayhello: # invokes the parameterized job
          saywhat: Everyone

workflows:
  build:
    jobs:
      - sayhello:
          name: build-sayhello
          saywhat: Everyone
  deploy:
    jobs:
      - sayhello:
          name: deploy-sayhello
          saywhat: All

Jobs defined in an orb

If a job is declared inside an orb it can use commands in that orb or the global commands. It is not possible to call commands outside the scope of declaration of the job.

hello-orb

version: 2.1
# partial yaml from hello-orb
jobs:
  sayhello:
    parameters:
      saywhat:
        description: "To whom shall we say hello?"
        default: "World"
        type: string
    docker:
      - image: cimg/base:2023.11
    steps:
      - saywhat:
          saywhat: "<< parameters.saywhat >>"
commands:
  saywhat:
    parameters:
      saywhat:
        type: string
    steps:
      - run: echo "<< parameters.saywhat >>"

Config leveraging hello-orb

# config.yml
version: 2.1
orbs:
  hello-orb: somenamespace/hello-orb@volatile
workflows:
  build:
    jobs:
      - hello-orb/sayhello:
          saywhat: Everyone

Using parameters in executors

To use parameters in executors, define the parameters under the given executor. When you invoke the executor, pass the keys of the parameters as a map of keys under the executor: declaration, each of which has the value of the parameter to pass in.

Parameters in executors can be of the type string, enum, or boolean. Default values can be provided with the optional default key.

Example build configuration using a parameterized executor

version: 2.1
executors:
  python:
    parameters:
      tag:
        type: string
        default: latest
      myspecialvar:
        type: string
    docker:
      - image: cimg/python:<< parameters.tag >>
    environment:
      MYPRECIOUS: << parameters.myspecialvar >>
jobs:
  build:
    executor:
      name: python
      tag: "2.7"
      myspecialvar: "myspecialvalue"

The above would resolve to the following:

version: 2.1
jobs:
  build:
    steps: []
    docker:
      - image: cimg/python:2.7
    environment:
      MYPRECIOUS: "myspecialvalue"

The scope of parameters

Parameters are in-scope only within the job or command that defined them. If you want a job or command to pass its parameters to a command it invokes, they must be passed explicitly.

version: 2.1
jobs:
  sayhello:
    parameters:
      saywhat:
        description: "To whom shall we say hello?"
        default: "World"
        type: string
    docker:
      - image: cimg/base:2023.11
    steps:
      - say:
          # Since the command "say" doesn't define a default
          # value for the "saywhat" parameter, it must be
          # passed in manually
          saywhat: << parameters.saywhat >>
commands:
  say:
    parameters:
      saywhat:
        type: string
    steps:
      - run: echo "<< parameters.saywhat >>"
workflows:
  build:
    jobs:
      - sayhello:
          saywhat: Everyone

Invoking the same job multiple times

A single configuration may invoke a job multiple times. At configuration processing time during build ingestion, CircleCI will auto-generate names if none are provided or you may name the duplicate jobs explicitly with the name key.

version: 2.1
workflows:
  build:
    jobs:
      - loadsay
      # This doesn't need an explicit name as it has no downstream dependencies
      - sayhello:
          saywhat: Everyone
          requires:
            - loadsay
      # This needs an explicit name for saygoodbye to require it as a job dependency
      - sayhello:
          name: SayHelloChad
          saywhat: Chad
      # Uses explicitly defined "sayhello"
      - saygoodbye:
          requires:
            - SayHelloChad

Using pre and post steps

Every job invocation may optionally accept two special arguments: pre-steps and post-steps. Steps under pre-steps are executed before any of the other steps in the job. The steps under post-steps are executed after all of the other steps.

Pre and post steps allow you to execute steps in a given job without modifying the job. This is useful, for example, in running custom setup steps before job execution.

Defining pre and post steps

The following example defines pre-steps and post-steps in the bar job of the build workflow:

# config.yml
version: 2.1
jobs:
  bar:
    docker:
      - image: cimg/base:2023.11
    steps:
      - checkout
      - run:
          command: echo "building"
      - run:
          command: echo "testing"
workflows:
  build:
    jobs:
      - bar:
          pre-steps:
            - run:
                command: echo "install custom dependency"
          post-steps:
            - run:
                command: echo "upload artifact to s3"

Defining conditional steps

Conditional steps run only if a condition is met at config-compile time, before a workflow runs. This means, for example, that you may not use a condition to check an environment variable, as those are not injected until your steps are running in the shell of your execution environment.

Conditional steps may be located anywhere a regular step could and may only use parameter values as inputs.

For example, an orb could define a command that runs a set of steps if invoked with myorb/foo: { dostuff: true }, but not myorb/foo: { dostuff: false }.

Furthermore, an orb author could define conditional steps in the steps key of a Job or a Command.

# Inside config.yml
version: 2.1
jobs:
  myjob:
    parameters:
      preinstall-foo:
        type: boolean
        default: false
    docker:
      - image: cimg/base:2023.11
    steps:
      - run: echo "preinstall is << parameters.preinstall-foo >>"
      - when:
          condition: << parameters.preinstall-foo >>
          steps:
            - run: echo "preinstall"
      - unless:
          condition: << parameters.preinstall-foo >>
          steps:
            - run: echo "don't preinstall"
workflows:
  workflow:
    jobs:
      - myjob:
          preinstall-foo: false
      - myjob:
          preinstall-foo: true
      - myjob # The empty string is falsy

The when step

Under the when key are the subkeys condition and steps. The subkey steps are run only if the condition evaluates to a truthy value.

KeyRequiredTypeDescription
conditionYLogic A logic statement
stepsYSequenceA list of steps to execute when the condition is truthy.

The unless step

Under the unless key are the subkeys condition and steps. The subkey steps are run only if the condition evaluates to a falsy value.

KeyRequiredTypeDescription
conditionYLogic A logic statement
stepsYSequenceA list of steps to execute when the condition is falsy.

Writing inline orbs

When defining reusable configuration elements directly within your config, you can also wrap those elements within an inline orb. You may find inline orbs useful for development or for name-spacing elements that share names in a local config.

To write an inline orb, place the orb elements under that orb’s key in the orbs declaration section of the configuration. For example, if you want to import one orb to use inside another inline orb, the config could look like the example shown below, in which the inline orb my-orb imports the node orb:

version: 2.1

orbs:
  my-orb:
    orbs:
      node: circleci/node@3.0
    commands:
      my_command:
        steps:
          - run: echo "Run my tests"
    jobs:
      my_job:
        executor: node/default # Node orb executor
        steps:
          - checkout
          - my_command
          - store_test_results:
              path: test-results

workflows:
  main:
    jobs:
      - my-orb/my_job

See also

  • Refer to Sample Configurations for some sample configurations that you can use in your own CircleCI configuration.
  • Refer to Database Examples for database examples you can use in your CircleCI configuration.

Suggest an edit to this page

Make a contribution
Learn how to contribute

Still need help?

Ask the CircleCI community
Join the research community
Visit our Support site