metrics.sh/metrics/memory.sh

#!/bin/sh

if is_osx; then
  start () {
    readonly __memory_os_memsize=$(sysctl -n hw.memsize)
  }

  collect () {
    report $(vm_stat | awk -v total_memory=$__memory_os_memsize \
            'BEGIN { FS="   *"; pages=0 }
            /Pages (free|inactive|speculative)/ { pages+=$2 }
            END { printf "%.1f", 100 - (pages * 4096) / total_memory * 100.0 }')
  }
else
  collect () {
    report $(free | awk '/buffers\/cache/ {
                              printf "%.1f", 100 - $4 / ($3 + $4) * 100.0 }')
  }
fi

docs () {
  echo "Percentage of used memory."
}