#!/bin/sh
#
# Created 3/31/19 in /usr/lib/systemd/system-sleep/
if [ "${1}" == "pre" ]; then
# Do the thing you want before suspend here, e.g.:
echo "we are suspending at $(date)..." > /tmp/systemd_suspend_test
elif [ "${1}" == "post" ]; then
# Do the thing you want after resume here, e.g.:
echo "...and we are back from $(date)" >> /tmp/systemd_suspend_test
gxmessage -fg red -font 'sans 30' -timeout 3 ' Computer has now resumed from suspend state.'
fi
"${1}" is the long form of "$1". It is the first positional parameter the script got. If you call a script like this:
$ ./somescript.sh first second third
then inside ./somescript.sh the variable "$1" would be set to "first", the variable "$2" would be set to "second" and "$3" would be set to "third". So this line is asking if the first parameter to the script equals "pre".
Whatever happens to be the shell /bin/sh on your system may or may not be able to handle this correctly..
Another thing to verify is that gxmessage needs to be installed and in your default search path in order for the script to work, since the PATH variable is not set inside that script.
SYSTEMD-SUSPEND.SERVICE(8) systemd-suspend.service SYSTEMD-SUSPEND.SERVICE(8)
NAME
systemd-suspend.service, systemd-hibernate.service, systemd-hybrid-sleep.service, systemd-suspend-then-hibernate.service, systemd-sleep - System
sleep state logic
SYNOPSIS
systemd-suspend.service
systemd-hibernate.service
systemd-hybrid-sleep.service
systemd-suspend-then-hibernate.service
/lib/systemd/system-sleep
DESCRIPTION
systemd-suspend.service is a system service that is pulled in by suspend.target and is responsible for the actual system suspend. Similarly,
systemd-hibernate.service is pulled in by hibernate.target to execute the actual hibernation. Finally, systemd-hybrid-sleep.service is pulled in by
hybrid-sleep.target to execute hybrid hibernation with system suspend and pulled in by suspend-then-hibernate.target to execute system suspend with
a timeout that will activate hibernate later.
Immediately before entering system suspend and/or hibernation systemd-suspend.service (and the other mentioned units, respectively) will run all
executables in /lib/systemd/system-sleep/ and pass two arguments to them. The first argument will be "pre", the second either "suspend",
"hibernate", "hybrid-sleep", or "suspend-then-hibernate" depending on the chosen action. Immediately after leaving system suspend and/or
hibernation the same executables are run, but the first argument is now "post". All executables in this directory are executed in parallel, and
execution of the action is not continued until all executables have finished.
Note that scripts or binaries dropped in /lib/systemd/system-sleep/ are intended for local use only and should be considered hacks. If applications
want to react to system suspend/hibernation and resume, they should rather use the Inhibitor interface[1].
Note that systemd-suspend.service, systemd-hibernate.service, and systemd-hybrid-sleep.service systemd-suspend-then-hibernate.service should never
be executed directly. Instead, trigger system sleep states with a command such as "systemctl suspend" or similar.
Internally, this service will echo a string like "mem" into /sys/power/state, to trigger the actual system suspend. What exactly is written where
can be configured in the "[Sleep]" section of /etc/systemd/sleep.conf or a sleep.conf.d file. See systemd-sleep.conf(5).
OPTIONS
systemd-sleep understands the following commands:
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
suspend, hibernate, hybrid-sleep, suspend-then-hibernate
Suspend, hibernate, suspend then hibernate, or put the system to hybrid sleep.
SEE ALSO
systemd-sleep.conf(5), systemd(1), systemctl(1), systemd.special(7), systemd-halt.service(8)
NOTES
1. Inhibitor interface
https://www.freedesktop.org/wiki/Software/systemd/inhibit
systemd 237 SYSTEMD-SUSPEND.SERVICE(8)