#!/bin/bash
# Emits {"mem":<pct>} — memory usage percent, read straight from /proc/meminfo.
set -uo pipefail

mem_total=0
mem_avail=0
while read -r key value _; do
    case "$key" in
    MemTotal:) mem_total=$value ;;
    MemAvailable:) mem_avail=$value ;;
    esac
done </proc/meminfo

mem_pct=0
if ((mem_total > 0)); then
    mem_pct=$(awk -v t="$mem_total" -v a="$mem_avail" 'BEGIN { printf "%.0f", (t-a)/t*100 }')
fi

printf '{"mem":%s}\n' "$mem_pct"