Power Status (was Re: Because LC can't do two things at once.)

[Richard Gaskin]

Peter M. Brigham wrote:

 > On Mar 1, 2015, at 3:16 PM, Richard Gaskin wrote:

 >> Thanks to the beautiful simplicity of the Linux /proc directory
 >> I was able to find:
 >>
 >>    cat /proc/acpi/battery/BAT1/state
 >>
 >> The "charging state" field there will contain "charging" or
 >> "discharging".
 >
 > Question: this looks like a file on disk. I didn't know what you
 > meant by the "'charging state' field." What is the format of the
 > file? Is this a text file, an XML file, or something else?

One of the guiding design principles of Unix is "everything is a file", 
which allows us to access not only those byte streams that are actual 
files, but also system and process info such as that commonly mounted at 
/proc, all with the same common tools (cd, ls, cat, grep, more, less, 
etc.) - this page explains it well:
<http://en.wikipedia.org/wiki/Everything_is_a_file>

Being a certified Unix OS X probably has a /proc, but some Unix flavors 
don't mount it; most Linux distros do.


 > If you could give me a sample to look at I can parse it to get
 > the info and complete the handler. I don't have a linux system
 > to work with for this.

In my brief searching on this there were two files commonly noted, the 
one shown above and also /BAT0/state.  I'm not exactly sure why my 
laptop has a BAT1 but not a BAT0, and I'll see what I can turn up.

That said, given the increasing role of servers in our connected world, 
I can't say enough encouraging things about putting together a VM with 
Linux in it.  Tons of fun, very educational, and you can't beat the price.

And if you're a history buff, there's a version of Debian with OpenStep 
pre-installed so you can explore the look-and-feel of NeXT. :)


Michael Doub wrote:
 > I don't know if this helps since the only linux system i have is a
 > raspberryPi, but I get a file not found message when typing cat
 > /proc/acpi/battery/BAT1/state in a terminal window.

Thanks for trying that, Michael.

It may be helpful to also check for BAT0, but it may also be that 
because the Pi doesn't ship with a battery that's not normally part of 
the info the system provides.

While battery packs are available for Pi*, the device itself doesn't 
distinguish it from running on a wall socket; it's not integrated with 
battery monitoring firmware like laptops are.

If that hunch is correct, the absence of a battery info element in /proc 
may be an accurate reflection of the system state.

I'll do some more digging and see what I can find....



* I've been looking for a Pi case with an integrated battery pack.  I've 
seen several battery packs as separate cases, but I'd really prefer 
everything in one box.  Anyone here seen one?

-- 
  Richard Gaskin
  Fourth World Systems
  Software Design and Development for the Desktop, Mobile, and the Web
  ____________________________________________________________________
  Ambassador at FourthWorld.com                http://www.FourthWorld.com