How do I implement an Automated Emergency Suspend or Shutdown?

[Moderator BobC]

If my system is running on battery and its running low, I have an alert script running from cron to notice the problem and sound an alarm. But if the battery level is so low that its critical, I would like the system to do a shutdown on its own without me being there to type any keys.

How can I do that?

[Moderator christophe]

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These looks promising:
https://superuser.com/questions/1057868/shutdown-a-linux-computer-depending-on-the-battery-level
https://unix.stackexchange.com/questions/84437/how-do-i-make-my-laptop-sleep-when-it-reaches-some-low-battery-threshold

confirmed antiX frugaler, since 2019

[Member iznit]

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BobC, you should get a good result from combining the scripted ideas in these linked pages
https://unix.stackexchange.com/questions/84437/how-do-i-make-my-laptop-sleep-when-it-reaches-some-low-battery-threshold
https://wiki.archlinux.org/title/laptop#hibernate_on_low_battery_level
http://mindspill.net/computing/linux-notes/acpi/acpi-low-battery-warning/
https://www.geeksforgeeks.org/bash-script-to-get-low-battery-alert-in-linux/

I would choose to include a boolean AND for the triggering logic
“only if AC power is not connected && …..”

[Moderator BobC]

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The first requires sudo

I will try the 2nd. Maybe running the cron job as root will make it work.

Thanks

[Moderator BobC]

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Ok, this works running from cron as root, except one thing. I get all the messages and sounds, but the system doesn’t shutdown. Any ideas?

#!/bin/bash

# lowbattery-check - low battery check and alarm
# runs from root crontab

TOO_LOW=50 # how low is too low?
CRITICALLY_LOW=40 # initiate shutdown
LOW_TIME_REM=00:15:00

export DISPLAY=:0.0

BATTERY_LEVEL=$(acpi -b | grep -P -o '[0-9]+(?=%)')
STATUS=$(acpi --b)

BATTINFO=<code>acpi -b</code>
echo "$(date) lowbattery-check ran, status: $STATUS   battinfo: $BATTINFO" >> /home/bobc/bin/lowbattery-check.log
if [[ <code>echo $BATTINFO | grep Discharging</code> ]]; then
  echo "$(date) lowbattery-check battery discharging: $STATUS" >> /home/bobc/bin/lowbattery-check.log
  if [[ $BATTERY_LEVEL -lt $TOO_LOW ]]; then
    echo "$(date) lowbattery-check battery too low: $BATTERY_LEVEL" >> /home/bobc/bin/lowbattery-check.log
    espeak "BATTERY TOO LOW!" \
	&& play /usr/lib/libreoffice/share/gallery/sounds/ups.wav \
	&& play /usr/lib/libreoffice/share/gallery/sounds/untie.wav \
	&& play /usr/lib/libreoffice/share/gallery/sounds/ups.wav \
	&& yad --no-buttons --center --borders=22 --timeout=10 --title="BATTERY LOW" --text="Plug computer in NOW"
  if [[ $BATTERY_LEVEL -lt $CRITICALLY_LOW ]]; then
      echo "$(date) lowbattery-check battery CRITICALLY low, SHUTDOWN: $BATTERY_LEVEL" >> /home/bobc/bin/lowbattery-check.log
      espeak "BATTERY CRITICALLY LOW, SHUTDOWN INITIATED!" \
      && play /usr/lib/libreoffice/share/gallery/sounds/ups.wav \
	  && play /usr/lib/libreoffice/share/gallery/sounds/untie.wav \
	  && play /usr/lib/libreoffice/share/gallery/sounds/ups.wav \
	  && yad --no-buttons --center --borders=22 --title="BATTERY CRITICALLY LOW" --text="SHUTDOWN INITIATED" \
      && desktop-session-exit --shutdown
    fi    
  fi
fi

exit 0

[Moderator christophe]

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Instead of desktop-session-exit --shutdown
try poweroff or halt

Does that work?

confirmed antiX frugaler, since 2019

[Member iznit]

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if [[ $BATTERY_LEVEL -lt $CRITICALLY_LOW ]]; then
Well the commands don’t need to be boolean chained all on one line.
Easier debug if they are separate.

echo yahdahyahdah
espeak yahdahyahdah
play yahdahyahdah
play yahdahyahdah
play yahdahyahdah
yad yahdahyahdah
/full/path/to/desktop-session-exit yahdahyahdah

And full path because the rooty shell in which the cronned script is running in may not have $PATH you expect. Also the environment [variables] of this shell may lack one/several envvars needed by expected by desktop-session-exit. As a debug test, does plain ole “shutdown” command work here?

Might also wanna change the logic to an if [critical] elif [too low] instead of deep nesting.

[Moderator christophe]

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iznit wrote:

/full/path/to/desktop-session-exit yahdahyahdah

And full path because …

I like that. Makes sense to me…

confirmed antiX frugaler, since 2019

[Moderator BobC]

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Yes, good points, all. I had copied many snips of code from many places and put them together like a Frankenstein monster, which didn’t work quite right, LOL.

Revised code:

#!/bin/bash

# lowbattery-check - low battery check and alarm
# runs from root crontab

# requires espeak and libreoffice for audible alerts

TOO_LOW=50 # how low is too low?
CRITICALLY_LOW=40 # initiate shutdown
LOW_TIME_REM=00:15:00

export DISPLAY=:0.0

BATTERY_LEVEL=$(acpi -b | grep -P -o '[0-9]+(?=%)')
STATUS=$(acpi --b)

BATTINFO=<code>acpi -b</code>
echo "$(date) lowbattery-check ran, status: $STATUS   battinfo: $BATTINFO" >> /home/bobc/bin/lowbattery-check.log
if [[ <code>echo $BATTINFO | grep Discharging</code> ]]; then
  echo "$(date) lowbattery-check battery discharging: $STATUS" >> /home/bobc/bin/lowbattery-check.log
  if [[ $BATTERY_LEVEL -lt $TOO_LOW ]]; then
    echo "$(date) lowbattery-check battery too low: $BATTERY_LEVEL" >> /home/bobc/bin/lowbattery-check.log
    espeak "BATTERY TOO LOW!"
	play /usr/lib/libreoffice/share/gallery/sounds/ups.wav
	play /usr/lib/libreoffice/share/gallery/sounds/untie.wav
	play /usr/lib/libreoffice/share/gallery/sounds/ups.wav
	yad --no-buttons --center --borders=22 --timeout=10 --title="BATTERY LOW" --text="Plug computer in NOW"
  if [[ $BATTERY_LEVEL -lt $CRITICALLY_LOW ]]; then
      echo "$(date) lowbattery-check battery CRITICALLY low, SHUTDOWN: $BATTERY_LEVEL" >> /home/bobc/bin/lowbattery-check.log
      espeak "BATTERY CRITICALLY LOW, SHUTDOWN INITIATED!"
      play /usr/lib/libreoffice/share/gallery/sounds/ups.wav
      play /usr/lib/libreoffice/share/gallery/sounds/untie.wav
      play /usr/lib/libreoffice/share/gallery/sounds/ups.wav
      yad --no-buttons --center --borders=22 --title="BATTERY CRITICALLY LOW" --text="SHUTDOWN INITIATED"
      /usr/sbin/halt -p
    fi    
  fi
fi
exit 0

• This reply was modified 8 months ago by BobC. Reason: had to use /usr/sbin/halt -p

[Moderator BobC]

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I will clean it up, more. I want it to be configurable. I might base it on battery minutes left rather than percent. This one is only lasting 30 minutes or so, but it is very optimistic in the beginning.

[Member sybok]

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Hi @BobC, I did some cleaning and restructuring of the code. Hope that helps you.

BTW, I dare to suggest to check first for the critically low level not to get into both low and then critically low.
Unless this is intended design.

Please see below

#!/bin/bash

###############################################################################
## lowbattery-check - low battery check and alarm
## runs from root crontab
##
## requires espeak and libreoffice-files for audible alerts
###############################################################################

TOO_LOW=50 # how low is too low?
CRITICALLY_LOW=40 # initiate shutdown
LOW_TIME_REM=00:15:00

export DISPLAY=:0.0

# Array of sounds to play:
re_sound=('/usr/lib/libreoffice/share/gallery/sounds/ups.wav' '/usr/lib/libreoffice/share/gallery/sounds/untie.wav' '/usr/lib/libreoffice/share/gallery/sounds/ups.wav')

log_file='/home/bobc/bin/lowbattery-check.log'

# Placeholders:
BATTINFO=''
BATTERY_LEVEL=''
STATUS=''

get_battery(){
  # Update/Refresh battery info:
  BATTINFO=<code>acpi -b</code>
  BATTERY_LEVEL=$(acpi -b | grep -P -o '[0-9]+(?=%)')
  STATUS=$(acpi --b)
} # get_battery

play_sounds(){
  # Play configured sounds:
  local count_it

  count_it=0
  for one_file in "${re_sound[@]}"; do
    if ! [ -f "${one_file}" ]; then
      continue
    fi
    play "${one_file}"
    count_it=$((count_it + 1))
  done

  if [ "${count_it}" == "0" ]; then
    # Fall-back sound, ring the system bell, see [https://superuser.com/questions/969080]
    tput bel || echo -e "\07"
  fi
} # play_sounds

run_checked(){
  # Run the check of battery:
  echo "$(date) lowbattery-check ran, status: [${STATUS}] battinfo: [${BATTINFO}]" >> "${log_file}"
  if [[ -z "$(echo "${BATTINFO}" | grep 'Discharging')" ]]; then
    # Charging, nothing to do, return = exit this function
    return
  fi

  echo "$(date) lowbattery-check battery discharging: ${STATUS}" >> "${log_file}"
  if [[ "${BATTERY_LEVEL}" -lt "${TOO_LOW}" ]]; then
    echo "$(date) lowbattery-check battery too low: [${BATTERY_LEVEL}]" >> "${log_file}"
    espeak "BATTERY TOO LOW!"
    play_sounds
    # TODO: Is it possible to make it stick/appear at all desktops?
    yad --no-buttons --center --borders=22 --timeout=10 --title="BATTERY LOW" --text="Plug computer in NOW"
  fi
  if [[ "${BATTERY_LEVEL}" -lt "${CRITICALLY_LOW}" ]]; then
    echo "$(date) lowbattery-check battery CRITICALLY low, SHUTDOWN: [${BATTERY_LEVEL}]" >> "${log_file}"
    espeak "BATTERY CRITICALLY LOW, SHUTDOWN INITIATED!"
    play_sounds
    # TODO: Is it possible to make it stick/appear at all desktops?
    yad --no-buttons --center --borders=22 --title="BATTERY CRITICALLY LOW" --text="SHUTDOWN INITIATED"
    /usr/sbin/halt -p
  fi
} # run_checked

main(){
  # Main function:
  get_battery
  run_checked
  exit 0
} # main

main

[Moderator BobC]

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As I’d said, I was reworking the program last night, and did get that done.

Yes, there were a number of inconsistencies in my program caused by taking different ideas from multiple programs and trying to assemble them into one program, and also make it work.

At lunch today, I incorporated a number of your ideas.

One I didn’t understand was surrounding the variables:
“${BATTERY_LEVEL}”
I hadn’t seen that before. Could you explain the purpose, please?

[Member iznit]

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${MYVARIABLE}
BobC, this is the syntax for Shell Parameter Expansion

[Moderator BobC]

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Shell parameter expansion is a new term to me. It does make sense, and I have encountered the problem before where I wanted the value of a variable to be followed immediately by another value. It makes me wonder why all bash programs aren’t written using that syntax. I will have to see if that syntax is also allowed at work (where I am the only programmer that uses the shell tools, so have no mentor or examples).

And yes, sybok, my logic is based on there being 2 levels. One where we need to warn them that the battery is discharging and getting low, and ask them to plug it in. And the second is where the situation is critical, and if they don’t plug it in immediately, we need to shutdown to avoid possible data loss and/or corruption.

In the end, I decided to base it on battery power remaining expressed as time remaining in seconds, and set the warning level at 15 minutes (900 seconds) by default, and the critical level at 5 minutes (300 seconds) by default. I would like to have the user’s selected values maintained and stored somewhere with a little YAD script, I think. The idea was to then retrieve/use them to give user level warnings as well as the root level critical warnings and actions.

Do you think that makes it sense to have 2 separate programs running from cron for that, or do you think it would be better to combine them into one program and run it under root so it is able to shutdown if needed? I’m starting to think that they should be combined and have fewer program files, and only one cron job to run.

Thanks to both of you for adding another bit of syntax knowledge to my storage cells.

[Member sybok]

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@BobC: Options to make it more configurable.
That reminds me of a topic with @ModdIt where he/we tried to make ‘/etc/hosts’ per user. Some multi-user issues were encountered. I do not know what is the current status (got out of touch).

1) I assume that the suggested “split” would mean the following two items apply:
A) common global configuration (better be placed in a configuration file so that upgrade asks whether to overwrite any local changes)
B) local configuration for non-critical warnings per user that each corresponding user can edit.

– How does the script recognize which local/user configuration is to be loaded? Test for user/users that is/are logged in.
– Does remote access e.g. via SSH apply? (How to display the warning in this case?)
– What if multiple users are logged in? E.g. a local user and a remote VNC user; is there any preference or does it run for all logged-in users that have the local configuration file?

2) Single script or two scripts?
I believe that a single script is better option.
One can define functions in it and have it structured e.g. as follows:

load_ini_file(){
  # Load thresholds from current ini file into placeholders thus refreshing them
  local ini_file
  ini_file="$*"

  # Load the thresholds: grep line; awk no. 1: get value (with comment(s)); awk no. 2: strip comment(s), if any; xargs: strip white-spaces
  <variable to store the value>="$(grep '^[ ]*<threshold name>[ ]*=[ ]*' "${ini_file}" | awk -F= ' { print $2 } ' | awk -F# ' { print $1 } ' | xargs)"
} # load_ini_file

run_one_check(){ 
  # Run a check based on passed configuration file
  local ini_file
  ini_file="$*"
  if ! [ -f "${ini_file}" ]; then
    return
  fi
  load_ini_file "${ini_file}"
  # Continue with the check ...

} # run_one_check
iterate_check(){
  # Iterate over configuration files:
  # 1) Get list of local files: use the global and local variations, e.g. logged in users-array and
  #    /home/${log_user}/.desktop-session/power-check.ini <-- FIXME: user may have its home at a different path!
  # 2) Use/Add the global file as well, e.g. global_ini='/etc/opt/power_check/power-check.ini'
  # 3) Iterate over these files

  for one_user in ${sysusers}; do
    if [ <user logged in> ]; then
      run_one_check "<home of user>/.desktop-session/power-check.ini"
    fi
  done
  run_one_check "${global_ini}"
} # iterate_check

main(){
  iterate_check
  exit 0
} # main

main

3) Where does it log in the case of multiple users? Should the file be readable by all/other users?

4) BTW, I have discovered a tool ‘shellcheck’ that performs syntax check of your scripts.
It can provide useful hints but sometimes its suggestions to double-quote variables to avoid expansion can cause troubles.

I usually output the results of the analysis into a file as follows ‘j=script.sh; shellcheck “$j” > “shell_$j”‘.

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