Can I get the status of a process by using the HDD and Power LEDs as indicators?
I'd like to use the green power LED to tell me that a status is available, and the red LED to tell me that it isn't.
On a linux box, you can see and affect the state & brightness of various LED's through the /sys/class/leds subdirectories.
On my system:
Let's look in the ath5k-phy0::rx subdir:
If you examine the contents of the files shown, it gets interesting.
look in trigger, you can see what 'built-in' triggers are available, and which one is currently in use:
Find the entry with the square brackets (towards the right), it shows that this LED is being controlled at the moment by the wireless receiver status. It glows orange (on this system) when it receives a packet.
You can echo a name to this trigger file to change what controls it. Want to show when the battery is charging-or-full?
If you set the controller to none, then YOU can output values to the brightness file to control the on/off of the LED.
Always good to refer to the kernel documentation for more information. GIYF
I've played with this in the past, but nothing real recent. What LED's are available are solely based on your hardware and kernel drivers/modules. YMMV.
HDD leds are normally tied to the hard drive controller. There isn't a way for an operating system on a PC to make it light up other than by causing some hard drive activity. Neither accessible to the OS is the power led.
What's easier is to use the keyboard LEDs for this purpose. Since you are indicating Ubuntu in your tags, you may want to look at a program called