Question

Ok, so it’s been a while, and i’m having problems with #includes

So I’m doing

#include "someheader.h"

but it’s giving me

fatal error: someheader.h: No such file or directory

It’s a system wide library I guess you could say.
I’m running arch linux and I installed the library from the repo, and I think the .h files are in /usr/include.

I could just copy all the header files into the folder my code is in but that would be a hack.

What is the “right” way to do this?

Edit: I wasn’t correct by saying the .h files were in /usr/include, what I meant was that the library folder was in there
So, Emile Cormier’s answer worked to a certain extent.
The problem now is that there are some include in the header file and it seems from the methods I’m trying to access that those includes are not happening
it’s giving my the error

undefined reference to Namespace::Class::method()

Edit:
Ok so the final answer is:

#include <library_name/someheader.h>

And compile with

g++ code.cpp -llibrary_name

Answer 1

Sometimes, header files for a library are installed in /usr/include/library_name, so you have to include like this:

#include <library_name/someheader.h>

Use your file manager (or console commands) to locate the header file on your system and see if you should prefix the header’s filename with a directory name.

---

The undefined reference error you’re getting is a linker error. You’re getting this error because you’re not linking in libsynaptics along with your program, thus the linker cannot find the "implementation" of the libsynaptics functions you’re using.

If you’re compiling from the command-line with GCC, you must add the -lsynaptics option to link in the libsynaptics library. If you’re using an IDE, you must find the place where you can specify libraries to link to and add synaptics. If you’re using a makefile, you have to modify your list of linker flags so that it adds -lsynaptics.

Also the -L <path_to_library> flag for the search path needs to be added, so the linker can find the library, unless it’s installed in one of the standard linker search paths.

See this tutorial on linking to libraries with GCC.