Calculate up time percentage using journalctl

calc_uptime.sh

#!/bin/bash

function get_stime() {
  head -n 2 <<< "$1" | tail -n 1 | cut -d ' ' -f 1-3 | date --date="$(cat /dev/fd/0)" +%s 
}

function get_etime() {
  tail -n 1 <<< "$1" | cut -d ' ' -f 1-3 | date --date="$(cat /dev/fd/0)" +%s 
}

declare -i boot=0
declare -i up_time=0
declare -i last_etime first_stime total_time stime etime
declare    juornal

while :; do
  journal="$(journalctl --boot $boot 2> /dev/null)" || break

  stime=$(get_stime "$journal")
  etime=$(get_etime "$journal")

  if [[ -z "$last_etime" ]]; then
    last_etime=$etime
  fi  

  : $[up_time += $(get_etime "$journal") - stime]

  : $[boot -= 1]
done

first_stime=$stime

total_time=$((last_etime - first_stime))

echo "$(bc -l <<< "100.0 * ($up_time / $total_time)" | sed 's/\(\.....\).*/\1/')%"

# vim: set ts=2 sw=2 et syn=sh: