How do I get hardware information on Linux/Unix?
If you need a simple answer, use:
cat /proc/cpuinfocat /proc/meminfolspcilsusb
and harvest any info you need from the output of these commands. (Note: the cut command may be your friend here if you are writing a shell script.)
Should you need more detail, add a -v switch to get verbose output from the lspci and lsusb commands.
If what you are looking for is a more feature-complete API, then use HAL, though that may be an overkill for what you are trying to build.