$ cat /proc/1/cgroup
0::/

def _is_in_docker() -> bool:
    try:
        with open('/proc/1/cgroup', 'rb') as f:
            return b'docker' in f.read()
    ...

def _get_container_id() -> str:
    ...
    with open('/proc/1/cgroup', 'rb') as f:
        for line in f.readlines():
            if line.split(b':')[1] == b'cpuset':
                return os.path.basename(line.split(b':')[2]).strip().decode()
    ...

$ rpm -qa |grep docker
docker-ce-cli-27.3.1-1.fc41.x86_64
docker-ce-27.3.1-1.fc41.x86_64
docker-ce-rootless-extras-27.3.1-1.fc41.x86_64
docker-compose-plugin-2.29.7-1.fc41.x86_64
docker-buildx-plugin-0.17.1-1.fc41.x86_64

$ rpm -qa |grep docker
docker-compose-plugin-2.29.7-1.fc40.x86_64
docker-buildx-plugin-0.17.1-1.fc40.x86_64
docker-ce-cli-27.3.1-1.fc40.x86_64

repos:
  - repo: local
    hooks:
      - id: shfmt
        name: shfmt
        # shfmt versions can be found here:
        #   https://hub.docker.com/r/mvdan/shfmt/tags
        entry: mvdan/shfmt:v3.8.0
        language: docker_image
        types: [shell]
        args: ["-w"]