Download the Linux library from the main GP3 page (http://www.awce.com/gp3.htm). When you unzip the file you'll find several .c and .h files along with a Linux makefile. The output of the make file will be a .o file, a shared library, and two demo programs (one that uses the .o and one that uses the shared library).
You can also use Java (see http://www.awce.com/gp3java.htm).
Here's the read me file from the C language library:
These are generic example libraries for the GP3 from AWC
Version 2 16 Dec 2009
Fixes a nasty bug in the setarg routine
To use these complie GP3LIB.C and ONE of the platform-specific files.
Make sure DEMO (in GP3LIB.C) is set to 1. To run the DEMO program use:
gp3lib /dev/com1 (for Cygwin)
gp3lib com1 (for Windows or old Cygwin)
gp3lib /dev/ttyS0 (for Linux)
Of course, you have to replace the serial port name with the right
value for your setup. Note under linux, the COM port must not be
listening for logins (getty, mgetty, agetty, etc.).
If you want to port the library, you should not have to change
anything but the platform specific file.
When you are ready to use the library, recompile with DEMO=0 and
either make a library or link the object files into your program.
Example for Linux compile:
gcc -o gp3lib gp3lib.c gp3linux.c
The Makefile is for Linux and builds the following
gp3demo - Demo program
gp3sodemo - Demo program using shared library
libgp3.so - Shared lib (make install as root to install)
gp3lib.c takes two defines: DEMO and MAKELIB to control
if the demo code is built and if the library code is built.