runningContainerId function

String? runningContainerId()

Returns the Docker container ID of the current process, or null.

Reads /proc/self/cgroup and looks for lines whose cgroup path starts with /docker/. The 64-character hex string that follows is the container ID.

Returns null if:

• /proc/self/cgroup does not exist (non-Linux platforms),
• the process is not running inside a Docker container, or
• any I/O error occurs.

Implementation

String? runningContainerId() {
  final cgroupFile = File('/proc/self/cgroup');
  if (!cgroupFile.existsSync()) {
    return null;
  }
  for (final line in cgroupFile.readAsLinesSync()) {
    final path = line.split(':').last;
    if (path.startsWith('/docker/')) {
      return path.substring('/docker/'.length);
    }
  }
  return null;
}