#!/bin/bash
OUTPUT="/var/lib/node_exporter/textfile_collector/shm_usage.prom"
TMP=$(mktemp)

echo "# HELP container_shm_usage_bytes Shared memory usage in bytes" > $TMP
echo "# TYPE container_shm_usage_bytes gauge" >> $TMP
echo "# HELP container_shm_size_bytes Shared memory total size in bytes" >> $TMP
echo "# TYPE container_shm_size_bytes gauge" >> $TMP

while IFS= read -r line; do
    pid=$(echo "$line" | awk '{print $1}')
    container=$(echo "$line" | awk '{print $2}' | tr -d '/')

    if [ "$pid" = "0" ] || [ -z "$pid" ]; then continue; fi

    df_out=$(nsenter -t "$pid" -m df -B1 /dev/shm 2>/dev/null | tail -1)
    total=$(echo "$df_out" | awk '{print $2}')
    used=$(echo "$df_out" | awk '{print $3}')

    if [ -n "$used" ] && [ -n "$total" ]; then
        echo "container_shm_usage_bytes{name=\"$container\"} $used" >> $TMP
        echo "container_shm_size_bytes{name=\"$container\"} $total" >> $TMP
    fi
done < <(docker ps -q | xargs docker inspect --format '{{.State.Pid}} {{.Name}}' 2>/dev/null)

mv $TMP $OUTPUT
chmod 644 $OUTPUT