I am trying to write a function to return all the GUIDs of the devices attached to the machine, as well as returning the BIOS Id. How would I achieve this? I can only seem to find ways of doing it on a windows machine, but not a linux.
Linux does not assign a GUID to everything. Hardware is identified by hardware-native means, e.g. USB and PCI devices are identifies by vendor and device ID (and serial number).
You can see what data the kernel offers by browsing /sys. I'd also check the source of tools like lspci and lsusb to get an idea on how one retrieves data programmatically (i.e. without parsing files in /sys).
There is, by the way, also a tool called dmidecode, that does operate directly on DMI data.