GitHub Actions environment variables have distinct scopes:

• Workflow
• Job
• Step

It’s trivial to set static environment variables in each of these scopes. Setting dynamic environment variables can be done for job and step scopes in a straightforward manner. Since jobs don’t normally interact without additional options, advanced techniques would be needed to make a dynamic workflow environment variable.

Workflow

Set static workflow environment variables in GitHub Actions by using env: at the top level of a “.github/workflows/ci.yml” file like:

name: ci

env:
  CTEST_PARALLEL_LEVEL: 4
  CMAKE_BUILD_PARALLEL_LEVEL: 4
  CMAKE_GENERATOR: Ninja
  CC: gcc

Job

Static job environment variables are set like:

jobs:

  windows:
    runs-on: windows-latest
    env:
      CMAKE_GENERATOR: Ninja
      CC: gcc

Dynamic job environment variables (such as appending to PATH) are done by writing to environment files. For example, to add “~/.local/bin” to PATH with job scope, do like the following examples (distinct behavior for Windows).

The steps after the “run:” stanzas have the new value for the environment variable.

Linux / macOS

    - run: echo "${HOME}/.local/bin" >> $GITHUB_PATH

Windows

Windows defaults to PowerShell, so the syntax is distinct from Unix shells:

    - run: echo "${HOME}/.local/bin" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append

Step

The syntax to set a step environment variable is quite similar to above:

    - run: cmake -B build
      env:
        CMAKE_GENERATOR: Ninja
        CC: gcc