CI Integration

cmakefmt is designed to be a zero-friction CI step. Use --check to fail the build when files are not formatted, or --in-place to auto-format and commit the result.

GitHub Actions

The official cmakefmt/cmakefmt-action installs the correct binary for the runner OS, adds it to PATH, and runs cmakefmt with sensible defaults. No Rust toolchain or Python environment is required on the runner.

The action exposes two high-level inputs that cover almost every workflow:

• mode selects what cmakefmt does: check (verify formatting), diff (verify and print a unified diff), fix (reformat in place), or setup (install only, do not run).
• scope selects which files are processed: all (the whole repository), changed (files modified since the base ref), or staged (Git-tracked files in the index).

The paths, since, version, and working-directory inputs cover the rest. Reach for args only when you need flags none of the structured inputs expose.

Strict whole-repo check (recommended starting point)

The default behaviour: run cmakefmt --check --report-format github . over the entire repository. The job fails on the first file that would change, and inline annotations on the pull request show exactly where.

- uses: actions/checkout@v6
- uses: cmakefmt/cmakefmt-action@v2

Changed-file check for incremental rollout

When adopting cmakefmt in an existing repository without reformatting every CMake file on day one, scope the check to files modified since the base ref:

- uses: actions/checkout@v6
  with:
    fetch-depth: 0   # required so the action can resolve the base ref
- uses: cmakefmt/cmakefmt-action@v2
  with:
    mode: diff
    scope: changed

On pull requests, scope: changed compares against origin/${{ github.base_ref }}. On push events, it compares against the push event’s before commit. The since input lets you override the base ref when you want to compare against, for example, the most recent tag.

Auto-format and commit

Reformat files on the runner and push the result back. Combine mode: fix with a commit step:

- uses: actions/checkout@v6
- uses: cmakefmt/cmakefmt-action@v2
  with:
    mode: fix
- name: Commit any reformat
  uses: stefanzweifel/git-auto-commit-action@v5
  with:
    commit_message: "chore: auto-format CMake files"

Install only, run yourself

When you want full control over the cmakefmt invocation, install the binary with mode: setup and run it directly:

- uses: cmakefmt/cmakefmt-action@v2
  with:
    mode: setup
- run: cmakefmt --check --report-format sarif . > cmakefmt.sarif

Pin a specific version

The action installs the latest release by default. To pin to a specific version (e.g. for reproducible CI on long-lived branches):

- uses: cmakefmt/cmakefmt-action@v2
  with:
    version: "1.5.0"

Monorepo subdirectory

When CMake files live under a subdirectory rather than the repository root, point the action at it with working-directory:

- uses: cmakefmt/cmakefmt-action@v2
  with:
    working-directory: cpp/

Full example

name: Format check

on: [push, pull_request]

jobs:
  cmakefmt:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - uses: cmakefmt/cmakefmt-action@v2

The complete list of inputs and outputs is documented in the cmakefmt-action README.

GitLab CI

Download the pre-built Linux binary directly from GitHub Releases:

cmakefmt:
  stage: lint
  image: ubuntu:latest
  before_script:
    - apt-get update -qq && apt-get install -y -qq curl
    - |
      LATEST=$(curl -sI https://github.com/cmakefmt/cmakefmt/releases/latest \
        | grep -i '^location:' \
        | sed 's|.*/tag/v||;s/[[:space:]]//g')
      curl -sSL \
        "https://github.com/cmakefmt/cmakefmt/releases/download/v${LATEST}/cmakefmt-x86_64-unknown-linux-musl.tar.gz" \
        | tar -xz -C /usr/local/bin
  script:
    - cmakefmt --check .

Or install via Cargo if you already have a Rust image:

cmakefmt:
  stage: lint
  image: rust:latest
  cache:
    paths:
      - $CARGO_HOME/bin/
  script:
    - cargo install cmakefmt-rust --quiet
    - cmakefmt --check .

Azure Pipelines

steps:
  - script: |
      LATEST=$(curl -sI https://github.com/cmakefmt/cmakefmt/releases/latest \
        | grep -i '^location:' \
        | sed 's|.*/tag/v||;s/[[:space:]]//g')
      curl -sSL \
        "https://github.com/cmakefmt/cmakefmt/releases/download/v${LATEST}/cmakefmt-${LATEST}-x86_64-unknown-linux-musl.tar.gz" \
        | tar -xz --strip-components=1 -C /usr/local/bin
    displayName: Install cmakefmt
  - script: cmakefmt --check .
    displayName: Check CMake formatting

Or with Cargo:

steps:
  - script: cargo install cmakefmt-rust --quiet
    displayName: Install cmakefmt
  - script: cmakefmt --check .
    displayName: Check CMake formatting

Bitbucket Pipelines

pipelines:
  default:
    - step:
        name: Check CMake formatting
        image: rust:latest
        caches:
          - cargo
        script:
          - cargo install cmakefmt-rust --quiet
          - cmakefmt --check .

Docker

Pre-built images are published to GitHub Container Registry on every release:

docker run --rm -v "$(pwd):/work" -w /work ghcr.io/cmakefmt/cmakefmt --check .

Or format a single file via stdin:

cat CMakeLists.txt | docker run --rm -i ghcr.io/cmakefmt/cmakefmt -

Pin a specific version:

docker run --rm -v "$(pwd):/work" -w /work ghcr.io/cmakefmt/cmakefmt:1.5.0 --check .

You can also build the image locally from the repository root:

docker build -t cmakefmt .

pre-commit

Add a local hook to your .pre-commit-config.yaml. This runs cmakefmt --check on every staged CMake file before the commit is created:

repos:
  - repo: local
    hooks:
      - id: cmakefmt
        name: cmakefmt
        language: system
        entry: cmakefmt --check
        files: '(CMakeLists\.txt|\.cmake)$'
        pass_filenames: true

Install the hook once per clone:

pre-commit install

You can also run it manually across all files:

pre-commit run cmakefmt --all-files

Check only changed files

When working on large repositories, limit formatting checks to files changed since a given ref to keep CI fast:

# Check files changed since the last tag
cmakefmt --check --changed v0.1.0

# Check only staged files (useful locally)
cmakefmt --check --staged