Querying the Power Status of a Linux Machine Programmatically - c++

Question

On a Windows(R) machine the following function can be used for querying the system power status of the machine:
BOOL WINAPI GetSystemPowerStatus(LPSYSTEM_POWER_STATUS lpSystemPowerStatus);
Is there something similar for a Linux machine?

Answer 1

On most linux systems a daemon named acpid runs all the time monitoring for ACPI events and normally logs info to /var/log/acpid or /var/log/messages. There is a manpage for it at http://linux.die.net/man/8/acpid. acpid stores current ACPI info in /proc/acpi although that's being relocated to /sys somewhere and /sys/power/state holds the current power state seen by catting it (cat /sys/power/state). More info about ACPI is at http://acpi.sourceforge.net/documentation/sleep.html. JCM mentioned a command line tool for ACPI status monitoring named AcpiTool available at http://sourceforge.net/projects/acpitool/. I built that on CentOS and it works fine. Just follow the instructions in its INSTALL file to install it -- it requires a C++ compiler, which is commonly on linux or if not install one using yum or apt.
dmidecode can do many kinds of queries for low level issues including system power supply and controls, see http://linux.die.net/man/8/dmidecode
In collaboration with freedesktop.org RedHat developed and provides DeviceKit-power pre RH7 which is called UPower starting with RH7. It consists of a daemon and command line tool. A manpage for it is at http://www.pkill.info/linux/man/1-upower/. The --dump option of the command line tool provides some useful info but rarely up to date. Maybe restarting the daemon would cause an update. Here is an example of the output from a CentOS 6 host:
ca:17: devkit-power --dump
Device: /org/freedesktop/DeviceKit/Power/devices/line_power_ACAD
native-path: /sys/devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0003:00/power_supply/ACAD
power supply: yes
updated: Tue Dec 23 20:28:27 2014 (866 seconds ago)
has history: no
has statistics: no
line-power
online: yes
Daemon:
daemon-version: 014
can-suspend: no
can-hibernate yes
on-battery: no
on-low-battery: no
lid-is-closed: no
lid-is-present: no
Most major PC vendors such as Dell and HP provide their own apps for power management and monitoring and I've found it is best to use them because they know how to query custom probes designed into the HW and print full diagnostics for their support team.

Answer 2

On My Ubuntu system I found this Information in /sys/class/power_suply/ADP1/online .
For example I used it in a script in an If statement with the following code:
if (( CPUBenutzung > 11 )) || ! (( $(cat /sys/class/power_suply/ADP1/online) )); then Stopmining ; fi
for me this worked fine and stopped the mining process allways when there was no power connected or I did use for some other reason all 12 threads of my notebook.