#!/bin/bash

# Cabecera
printf "%-25s %-25s %-20s\n" "Encendido" "Apagado" "Tiempo activo"
printf "%-25s %-25s %-20s\n" "----------" "--------" "--------------"

# Usamos `tac` para invertir el orden de `last -x`
last -x | tac | awk '
/reboot/ {
  boot = $6" "$7" "$8
  next
}
/shutdown/ && boot != "" {
  shut = $6" "$7" "$8
  cmd1 = "date -d \""boot"\" +%s"; cmd1 | getline t1; close(cmd1);
  cmd2 = "date -d \""shut"\" +%s"; cmd2 | getline t2; close(cmd2);
  delta = t2 - t1
  if (delta > 0) {
    h = int(delta / 3600)
    m = int((delta % 3600) / 60)
    s = delta % 60
    printf "%-25s %-25s %02d:%02d:%02d\n", boot, shut, h, m, s
    total += delta
  }
  boot = ""
}
END {
  h = int(total / 3600)
  m = int((total % 3600) / 60)
  s = total % 60
  printf "\n%-51s %02d:%02d:%02d\n", "Tiempo total encendido:", h, m, s
}'