Variables

About variables

You can use variables to store information that you want to reference in your workflow. You reference variables within a workflow step or an action, and the variables are interpolated on the runner machine that runs your workflow. Commands that run in actions or workflow steps can create, read, and modify variables.

You can set your own custom variables, you can use the default variables that GitHub sets automatically, and you can also use any other variables that are set in the working environment on the runner. Variables are case-sensitive.

Defining environment variables

To set a custom environment variable, you can define it using the env key in the workflow file. The scope of a custom variable set by this method is limited to the element in which it is defined. You can define variables that are scoped for:

• The entire workflow, by using env at the top level of the workflow file.
• The contents of a job within a workflow, by using jobs.<job_id>.env.
• A specific step within a job, by using jobs.<job_id>.steps[*].env.

name: Greeting on variable day

on:
  workflow_dispatch

env:
  DAY_OF_WEEK: Monday

jobs:
  greeting_job:
    runs-on: ubuntu-latest
    env:
      Greeting: Hello
    steps:
      - name: "Say Hello Mona it's Monday"
        run: echo "$Greeting $First_Name. Today is $DAY_OF_WEEK!"
        env:
          First_Name: Mona

You can access env variable values using runner environment variables or using contexts. The above example above shows three custom variables being used as environment variables in an echo command: $DAY_OF_WEEK, $Greeting, and $First_Name. The values for these variables are set, and scoped, at the workflow, job, and step level respectively. For more information on accessing variable values using contexts, see "Using contexts to access variable values."

Because runner environment variable interpolation is done after a workflow job is sent to a runner machine, you must use the appropriate syntax for the shell that's used on the runner. In this example, the workflow specifies ubuntu-latest. By default, Linux runners use the bash shell, so you must use the syntax $NAME. If the workflow specified a Windows runner, you would use the syntax for PowerShell, $env:NAME. For more information about shells, see "Workflow syntax for GitHub Actions."

Naming conventions for environment variables

When you set an environment variable, you cannot use any of the default environment variable names. For a complete list of default environment variables, see "Default environment variables" below. If you attempt to override the value of one of these default variables, the assignment is ignored.

Any new variables you set that point to a location on the filesystem should have a _PATH suffix. The GITHUB_ENV and GITHUB_WORKSPACE default variables are exceptions to this convention.

Using contexts to access variable values

Contexts are a way to access information about workflow runs, variables, runner environments, jobs, and steps. For more information, see "Contexts". There are many other contexts that you can use for a variety of purposes in your workflows. For details of where you can use specific contexts within a workflow, see "Context availability."

You can access environment variable values using the env context.

Using the env context to access environment variable values

In addition to runner environment variables, GitHub Actions allows you to set and read env key values using contexts. Environment variables and contexts are intended for use at different points in the workflow.

Runner environment variables are always interpolated on the runner machine. However, parts of a workflow are processed by GitHub Actions and are not sent to the runner. You cannot use environment variables in these parts of a workflow file. Instead, you can use contexts. For example, an if conditional, which determines whether a job or step is sent to the runner, is always processed by GitHub Actions. You can use a context in an if conditional statement to access the value of an variable.

env:
  DAY_OF_WEEK: Monday

jobs:
  greeting_job:
    runs-on: ubuntu-latest
    env:
      Greeting: Hello
    steps:
      - name: "Say Hello Mona it's Monday"
        if: ${{ env.DAY_OF_WEEK == 'Monday' }}
        run: echo "$Greeting $First_Name. Today is $DAY_OF_WEEK!"
        env:
          First_Name: Mona

In this modification of the earlier example, we've introduced an if conditional. The workflow step is now only run if DAYS_OF_WEEK is set to "Monday". We access this value from the if conditional statement by using the env context.

You will commonly use either the env or github context to access variable values in parts of the workflow that are processed before jobs are sent to runners.

Context	Use case	Example
env	Reference custom variables defined in the workflow.	${{ env.MY_VARIABLE }}
github	Reference information about the workflow run and the event that triggered the run.	${{ github.repository }}

Default environment variables

The default environment variables that GitHub sets are available to every step in a workflow.

We strongly recommend that actions use variables to access the filesystem rather than using hardcoded file paths. GitHub sets variables for actions to use in all runner environments.

Variable	Description
CI	Always set to true.
GITHUB_ACTION	The name of the action currently running, or the id of a step. For example, for an action, __repo-owner_name-of-action-repo. GitHub removes special characters, and uses the name __run when the current step runs a script without an id. If you use the same script or action more than once in the same job, the name will include a suffix that consists of the sequence number preceded by an underscore. For example, the first script you run will have the name __run, and the second script will be named __run_2. Similarly, the second invocation of actions/checkout will be actionscheckout2.
GITHUB_ACTION_PATH	The path where an action is located. This property is only supported in composite actions. You can use this path to access files located in the same repository as the action. For example, /home/runner/work/_actions/repo-owner/name-of-action-repo/v1.
GITHUB_ACTION_REPOSITORY	For a step executing an action, this is the owner and repository name of the action. For example, actions/checkout.
GITHUB_ACTIONS	Always set to true when GitHub Actions is running the workflow. You can use this variable to differentiate when tests are being run locally or by GitHub Actions.
GITHUB_ACTOR	The name of the person or app that initiated the workflow. For example, octocat.
GITHUB_API_URL	Returns the API URL. For example: http(s)://HOSTNAME/api/v3.
GITHUB_BASE_REF	The name of the base ref or target branch of the pull request in a workflow run. This is only set when the event that triggers a workflow run is either pull_request or pull_request_target. For example, main.
GITHUB_ENV	The path on the runner to the file that sets variables from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/work/_temp/_runner_file_commands/set_env_87406d6e-4979-4d42-98e1-3dab1f48b13a. For more information, see "Workflow commands for GitHub Actions."
GITHUB_EVENT_NAME	The name of the event that triggered the workflow. For example, workflow_dispatch.
GITHUB_EVENT_PATH	The path to the file on the runner that contains the full event webhook payload. For example, /github/workflow/event.json.
GITHUB_GRAPHQL_URL	Returns the GraphQL API URL. For example: http(s)://HOSTNAME/api/graphql.
GITHUB_HEAD_REF	The head ref or source branch of the pull request in a workflow run. This property is only set when the event that triggers a workflow run is either pull_request or pull_request_target. For example, feature-branch-1.
GITHUB_JOB	The job_id of the current job. For example, greeting_job.
GITHUB_PATH	The path on the runner to the file that sets system PATH variables from workflow commands. This file is unique to the current step and changes for each step in a job. For example, /home/runner/work/_temp/_runner_file_commands/add_path_899b9445-ad4a-400c-aa89-249f18632cf5. For more information, see "Workflow commands for GitHub Actions."
GITHUB_REF	The fully-formed ref of the branch or tag that triggered the workflow run. For workflows triggered by push, this is the branch or tag ref that was pushed. For workflows triggered by pull_request, this is the pull request merge branch. For workflows triggered by release, this is the release tag created. For other triggers, this is the branch or tag ref that triggered the workflow run. This is only set if a branch or tag is available for the event type. The ref given is fully-formed, meaning that for branches the format is refs/heads/<branch_name>, for pull requests it is refs/pull/<pr_number>/merge, and for tags it is refs/tags/<tag_name>. For example, refs/heads/feature-branch-1.
GITHUB_REPOSITORY	The owner and repository name. For example, octocat/Hello-World.
GITHUB_REPOSITORY_OWNER	The repository owner's name. For example, octocat.
GITHUB_RETENTION_DAYS	The number of days that workflow run logs and artifacts are kept. For example, 90.
GITHUB_RUN_ATTEMPT	A unique number for each attempt of a particular workflow run in a repository. This number begins at 1 for the workflow run's first attempt, and increments with each re-run. For example, 3.
GITHUB_RUN_ID	A unique number for each workflow run within a repository. This number does not change if you re-run the workflow run. For example, 1658821493.
GITHUB_RUN_NUMBER	A unique number for each run of a particular workflow in a repository. This number begins at 1 for the workflow's first run, and increments with each new run. This number does not change if you re-run the workflow run. For example, 3.
GITHUB_SERVER_URL	The URL of the GitHub Enterprise Server server. For example: https://HOSTNAME.
GITHUB_SHA	The commit SHA that triggered the workflow. The value of this commit SHA depends on the event that triggered the workflow. For more information, see "Events that trigger workflows." For example, ffac537e6cbbf934b08745a378932722df287a53.
GITHUB_WORKFLOW	The name of the workflow. For example, My test workflow. If the workflow file doesn't specify a name, the value of this variable is the full path of the workflow file in the repository.
GITHUB_WORKSPACE	The default working directory on the runner for steps, and the default location of your repository when using the checkout action. For example, /home/runner/work/my-repo-name/my-repo-name.
RUNNER_DEBUG	This is set only if debug logging is enabled, and always has the value of 1. It can be useful as an indicator to enable additional debugging or verbose logging in your own job steps.
RUNNER_NAME	The name of the runner executing the job. For example, Hosted Agent
RUNNER_OS	The operating system of the runner executing the job. Possible values are Linux, Windows, or macOS. For example, Windows
RUNNER_TEMP	The path to a temporary directory on the runner. This directory is emptied at the beginning and end of each job. Note that files will not be removed if the runner's user account does not have permission to delete them. For example, D:\a\_temp
RUNNER_TOOL_CACHE	The path to the directory containing preinstalled tools for GitHub-hosted runners. For more information, see "About GitHub-hosted runners". For example, C:\hostedtoolcache\windows

Detecting the operating system

You can write a single workflow file that can be used for different operating systems by using the RUNNER_OS default environment variable and the corresponding context property ${{ runner.os }}. For example, the following workflow could be run successfully if you changed the operating system from macos-latest to windows-latest without having to alter the syntax of the environment variables, which differs depending on the shell being used by the runner.

jobs:
  if-Windows-else:
    runs-on: macos-latest
    steps:
      - name: condition 1
        if: runner.os == 'Windows'
        run: echo "The operating system on the runner is $env:RUNNER_OS."
      - name: condition 2
        if: runner.os != 'Windows'
        run: echo "The operating system on the runner is not Windows, it's $RUNNER_OS."

In this example, the two if statements check the os property of the runner context to determine the operating system of the runner. if conditionals are processed by GitHub Actions, and only steps where the check resolves as true are sent to the runner. Here one of the checks will always be true and the other false, so only one of these steps is sent to the runner. Once the job is sent to the runner, the step is executed and the environment variable in the echo command is interpolated using the appropriate syntax ($env:NAME for PowerShell on Windows, and $NAME for bash and sh on Linux and MacOS). In this example, the statement runs-on: macos-latest means that the second step will be run.

Passing values between steps and jobs in a workflow

If you generate a value in one step of a job, you can use the value in subsequent steps of the same job by assigning the value to an existing or new environment variable and then writing this to the GITHUB_ENV environment file. The environment file can be used directly by an action, or from a shell command in the workflow file by using the run keyword. For more information, see "Workflow commands for GitHub Actions."

If you want to pass a value from a step in one job in a workflow to a step in another job in the workflow, you can define the value as a job output. You can then reference this job output from a step in another job. For more information, see "Workflow syntax for GitHub Actions."