Hello Simple!

Tuesday January 12 2021 12:14, you wrote to All:

 > I am working on a battery powered car and want the Pi to shut down
 > automatically if the battery starts to go flat to try to prevent SD
 > card corruption. I am a beginner to bash scripts! I will run this via
 > crontab...

 > #!/bin/bash
 > powerstatus=$(vcgencmd get_throttled)
 > if [ $powerstatus="throttled=0x1" ]
 > then
 > echo Under Voltage Detected - Shutting Down
 > sudo halt
 > else
 > echo Voltage Normal
 > fi

 > Obviously it is not working!! Could someone correct and explain for me
 > please.

You have another 2/3 possible issues :-

1.  crontab will only run the script at the defined point of time so you need
to run it often OR better still as a subtask from a routine that WILL run if
the battery is low at a given point (not almost flat) to shutdown the system ,
NOTE the term shutdown by using similar to shutdown -h now and not halt which
may well not close down any processes running first and possbly cause
curruptions on your system disk / SD etc.

2. As a follow on from 1 , you need a low level process that is constantly
running say with a sleep of nn seconds that tests the battery state and if 
good
sleeps or runs process similar to your bash script but not it and suggest say
a little C process as it would use less resources.

3. As a follow on from both of the above.
You should check what battery setting you have for throttled and have it set 
to
at least 25% battery power if you have a lot of proceses that can be running 
at
any one time and if needed a higher value.

I have a similar set of processes but linked to a APC UPS so see package
apcupsd.

Vincent

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