Xubuntu ACPI: The Lid

So what exactly does Xubuntu do when you close your laptop lid? acpid parses all the files in /etc/acpi/events for every file looking for an event= line that contains something that matches button/lid LID 00000080 00000005 or any part of it. On Xubuntu this would be /etc/acpi/events/lidbtn which calles /etc/acpi/lid.sh to handle this event.

So what exactly does /etc/acpi/lid.sh do? (The rest of this post goes line by line through /etc/acpi/lid.sh in chunks and explains what’s going on. Code from the script should be in mono spaced font and blockquoted.)

#!/bin/bash
 
. /usr/share/acpi-support/power-funcs
. /usr/share/acpi-support/policy-funcs
. /etc/default/acpi-support

These lines load some scripts containing utilities functions.

• . /usr/share/acpi-support/power-funcs – functions to get misc state info
• . /usr/share/acpi-support/policy-funcs – checks for GNOME/KDE power management programs
• . /etc/default/acpi-support – power conf file

 
[ -x /etc/acpi/local/lid.sh.pre ] && /etc/acpi/local/lid.sh.pre

This line looks for the executable file /etc/acpi/local/lid.sh.pre and runs the script if found. I assume this script is for personal user actions to be done before everything else since it does not exist by default.

if [ `CheckPolicy` == 0 ]; then exit; fi

This line checks for GNOME or KDE power managers running. If they are running the script trusts them take over and doesn’t do anything further.

grep -q closed /proc/acpi/button/lid/*/state
if [ $? = 0 ]
then

If the word “closed” is in /proc/acpi/button/lid/*/state this means that the laptop is shut and needs to do the following.

    for x in /tmp/.X11-unix/*; do
        displaynum=`echo $x | sed s#/tmp/.X11-unix/X##`
        getXuser;

To be continued…

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