btdtrigger 0.1.1

Simple utility to trigger commands when bluetooth devices are seen on Linux

Bluetooth Device Triggers

Simple Python utility that uses the scan functionality of bluetoothctl to trigger actions on a Linux machine based on nearby Bluetooth devices.

Requirements and Installation

This tool assumes your system meets the following requirements:

• python >= 3.11
• Linux
• bluetoothctl is installed (on my Arch system, this is provided by bluez-utils)
• You have a Bluetooth adapter

If those are met, this tool can be installed into a virtual environment with:

pip install btdtrigger

Usage

The basic idea of this utility is that it may be useful to have a Linux device do something when a particular Bluetooth device is seen. The initial inspiration for this was wanting a gaming PC to turn on remotely when a Bluetooth controller was powered on. Extending this to arbitrary commands is straightforward, so that is what we have here.

First, a simple example:

btdtrigger run-trigger --address 'AA:BB:CC:DD:EE' --status 'NEW' --command 'echo hello world!'

The above command defines a "trigger" which has two conditions and a command. The conditions are a mac address regex pattern and a device status. If those conditions are met, the specified command is run. So the above trigger will listen for a device with mac address AA:BB:CC:DD:EE that has the "NEW" status, which should happen if that device is powered on and searches for a connection. If those conditions are met, "hello world!" should be printed to the terminal.

Conditions: mac address patterns and status

Each trigger must match two conditions: a regex pattern for the device mac address, address, and a specified status. The address pattern can be any valid regex (and will ignore case). Some examples are:

• '.*' - match any address
• 'AA:BB:CC:DD:EE' - matches this mac address exactly
• 'AA.*' - matches any mac address starting with AA
• 'AA:BB:CC:DD:EE|11:22:33:44:55' - matches either of the given mac addresses

The status is simpler, it must be one of the following:

• 'NEW' - this status occurs when the listener sees a device that it didn't previously see (it is added to the list of devices in bluetoothctl)
• 'DEL' - this status occurs when a device previously in the list is no longer detectable, often from turning off or successfully connecting to another device and no longer advertising

So triggers that you want to run when a device is turned on, for example, would use the 'NEW' status. If you want the opposite behavior, where the trigger runs when no longer seen, you could use the 'DEL' status.

Commands and templates

The command to be run should be a valid shell command that can be run by the owner of the btdtrigger process. Under the hood it will be run as a subprocess.run, so the trigger listener process will wait for the command to complete before continuing to listen or run any other triggered commands.

Commands also support very limited templates, where attributes of the trigger or device can be injected into the command themselves. The following templates are supported:

• %address% - The mac address of the matched Bluetooth device
• %name% - The advertised name of the Bluetooth device
• %status% - The status condition of the trigger

For example, the following trigger definition will include the triggering devices mac address in the command in place of the %address% template and run against every new device seen.

btdtrigger run-trigger --address '.*' --status 'NEW' --command 'echo device %address% is new'

Running multiple triggers via a configuration file

In addition to the btdtrigger run-trigger command, where you define your trigger directly in the command itself, you can use the btdtrigger run command to execute triggers defined in a config.toml file as below:

[[triggers]]
device = ".*"
status = "NEW"
command = "echo device %address% is new"

This defines an identical trigger as used in the previous section and can be run with:

btdtrigger run -c config.toml

If a file is not provided via the -c option, it will default to ~/.config/btdtrigger/config.toml.

One benefit of defining triggers in a configuration file is the ability define multiple triggers together, which can be done by adding a new [[triggers]] block. We can update our config.toml to be:

[[triggers]]
device = ".*"
status = "NEW"
command = "echo device %address% is new"

[[triggers]]
device = ".*"
status = "DEL"
command = "echo device %address% is lost"

Running this should now echo out all the devices being seen and lost by the Bluetooth scan.