Ubuntu – Nothing happens when I close the lid or press power button

The number of processes should not be different. You have to remember when counting the pids to include the script itself and the subprocess created.

I created the following that should work for your requirements. You should alter the timeout depending on how quickly you want the multiple button presses.

#!/bin/sh
# /etc/acpi/powerbtn.sh
# Initiates a shutdown when the power putton has been
# pressed.

timeout=0.8
pid_count=$(pidof -x powerbtn.sh | wc -w)

( if [ $pid_count -eq 4 ]; then
        sleep $timeout
        /etc/acpi/sleep.sh
    else
        sleep $timeout
        pid_count_now=$(pidof -x powerbtn.sh | wc -w)
        if [ $pid_count_now -eq 2 ] && [ $pid_count -eq 2 ]; then
            poweroff
        fi
        exit
    fi
) &

1. Install pm-utils

   sudo apt-get install pm-utils
   

2. Reboot

Reference: [Solved] Issues with xfce4-power-manager-1.2.0

Discussion resume that: upower is relying on pm-utils to check for suspend/hibernate capability.

The broken link in the reference page should point to related bug report: Debian bug#639754 [upower] upower doesn't verify correctly the "suspend" and "hibernate" capabilities correctly

Not sure about this as upower package has Depends: pm-utils | systemd | systemd-services. I thought they should be alternatives. So may be there is other solution using systemd-services which is installed by default.