Genrule to check Linux sandbox

BUILD.bazel

genrule(
    name = "check_cgroup",
    outs = ["cgroup_output.txt"],
    cmd = """
        set -euo pipefail

        echo "==== /proc/self/cgroup ====" > $@
        cat /proc/self/cgroup >> $@
        echo "" >> $@

        echo "==== /proc/1/cgroup (init) ====" >> $@
        cat /proc/1/cgroup >> $@
        echo "" >> $@

        echo "==== /proc/self/mountinfo (filtered for cgroup) ====" >> $@
        grep cgroup /proc/self/mountinfo >> $@ || echo "(no cgroup mounts)" >> $@
        echo "" >> $@

        echo "==== Current PID ====" >> $@
        echo $$ >> $@
        echo "" >> $@

        echo "==== Kernel version ====" >> $@
        uname -a >> $@
        echo "" >> $@

        echo "==== Cgroup memory.max (current cgroup) ====" >> $@
        if [ -f /sys/fs/cgroup/memory.max ]; then
            cat /sys/fs/cgroup/memory.max >> $@
        else
            echo "/sys/fs/cgroup/memory.max not available" >> $@
        fi
        echo "" >> $@

        echo "==== Cgroup memory.max (/sys/fs/cgroup/example) ====" >> $@
        if [ -f /sys/fs/cgroup/example/memory.max ]; then
            cat /sys/fs/cgroup/example/memory.max >> $@
        else
            echo "/sys/fs/cgroup/example/memory.max not available" >> $@
        fi
        echo "" >> $@

        echo "==== Cgroup memory.max (/sys/fs/cgroup/example/child) ====" >> $@
        if [ -f /sys/fs/cgroup/example/child/memory.max ]; then
            cat /sys/fs/cgroup/example/child/memory.max >> $@
        else
            echo "/sys/fs/cgroup/example/child/memory.max not available" >> $@
        fi
        echo "" >> $@

        echo "==== Cgroup memory.max for each cgroup in /proc/self/cgroup ====" >> $@
        while IFS= read -r line; do
            IFS=: read -r _ _ cgroup_path <<< "$$line"
            if [ -f "/sys/fs/cgroup$${cgroup_path}/memory.max" ]; then
                echo "$${cgroup_path}: $$(cat /sys/fs/cgroup$${cgroup_path}/memory.max)" >> $@
            else
                echo "$${cgroup_path}: memory.max not available" >> $@
            fi
        done < /proc/self/cgroup
        echo "" >> $@
    """,
)