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cgroup

cgroup v2 unified-hierarchy readers. Linux-only — the table is empty on other platforms. Plan 18 / v0.15.1.

Pure std::fs reads with path canonicalisation; every input path is required to start with /sys/fs/cgroup/ after symlink resolution. Cgroup v2's "max" sentinel maps to Lua nil so callers can write if not mem.max then ... instead of comparing strings.

• cgroup.version() → "v2" | "v1" | "hybrid"
• cgroup.list(slice_path) → child cgroup directory names (filtered to entries that actually contain a cgroup.controllers file). Sorted.
• cgroup.cpu_stat(path) → {usage_usec, user_usec, system_usec, nr_periods, nr_throttled, throttled_usec, nr_bursts, burst_usec}
• cgroup.memory(path) → {current, max, swap_current, swap_max, peak, low, high, oom_kill, oom}
• cgroup.io(path) → [{device, rbytes, wbytes, rios, wios, dbytes, dios}, …]
• cgroup.pids(path) → {current, max}
• cgroup.procs(path) → list of pids in this cgroup

Typical usage: walk every container slice under /sys/fs/cgroup/machine.slice, read cpu_stat and memory once per refresh cycle, render a dashboard.