func SupportedSubsystems()

in cgroup/util.go [121:168]

• 34 lines of code
• 10 McCabe index (conditional complexity)

func SupportedSubsystems(rootfsMountpoint string) (map[string]struct{}, error) {
	if rootfsMountpoint == "" {
		rootfsMountpoint = "/"
	}

	cgroups, err := os.Open(filepath.Join(rootfsMountpoint, "proc", "cgroups"))
	if err != nil {
		if os.IsNotExist(err) {
			return nil, ErrCgroupsMissing
		}
		return nil, err
	}
	defer cgroups.Close()

	subsystemSet := map[string]struct{}{}
	sc := bufio.NewScanner(cgroups)
	for sc.Scan() {
		line := sc.Text()

		// Ignore the header.
		if len(line) > 0 && line[0] == '#' {
			continue
		}

		// Parse the cgroup subsystems.
		// Format:  subsys_name    hierarchy      num_cgroups    enabled
		// Example: cpuset         4              1              1
		fields := strings.Fields(line)
		if len(fields) == 0 {
			continue
		}

		// Check the enabled flag.
		if len(fields) > 3 {
			enabled := fields[3]
			if enabled == "0" {
				// Ignore cgroup subsystems that are disabled (via the
				// cgroup_disable kernel command-line boot parameter).
				continue
			}
		}

		subsystem := fields[0]
		subsystemSet[subsystem] = struct{}{}
	}

	return subsystemSet, sc.Err()
}