Auto halt and resume on power fluctuations

Ive only ever looked into it from an airpressure sensor perspective, but it should be close to the same thing
Here are my resources for it
forum.linuxcnc.org/10-advanced-configura...efore-doing-anything
forum.linuxcnc.org/49-basic-configuratio...xternal-safety-relay
maybe this one
forum.linuxcnc.org/10-advanced-configura...-pressure-monitoring

Coming back to this topic after having visited a few Chinese cnc router shops. All of them seem to have ability to continue from where power fail occured and job stopped due to this. None of them are using any power backup.

About power backup a decent size online ups would cost me almost same amount as my home made router.

Someone who has tried pls suggest. I am willing to work out with any of you to have a solution.

In my opinion this must be a default feature for any cnc and linuxcnc shall be able to process the gcode and be able to do initial one time setup and skip through the already executed code. A simple parser can be used to mark each line executed and on continue option it shall be able to analyse the gcode modules and be able to do initial spindle, feed changes and directly start executing the line which are not marked as executed.

Pls suggest...

First, you need a UPS or a laptop so the PC can stay on, otherwise this does not work.
Then use a relay that closes contacts when there is power, wire one contact to LinuxCNC feed-hold so it stops when power goes off.
Note the gcode line it stoped, shut down and wait for power to come back.
LinuxCNC has a feature to save the joint position on power failure so you can always know where is stopped.
It also has "run from line" as long as that line is not an arc.
Marlin writes to SD every line it is executing, so it can continue easily.
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We have ocasional power cuts, no UPS, nothing, just run from the line it stoped. On plenty of machines, so far never needed anything more.