Linking libusb in Mac OS X

Question

I have this very simple piece of code that I'm trying to compile. I'm fairly new to GCC from the command line, so please forgive me. I've tried a quite few different things with GCC, but I'm still unable to get it to compile. I do have libusb installed. How can I get this piece of code to compile?

Libusb:

anything:usb mymac$ brew list libusb
/usr/local/Cellar/libusb/1.0.9/include/libusb-1.0/libusb.h
/usr/local/Cellar/libusb/1.0.9/lib/libusb-1.0.0.dylib
/usr/local/Cellar/libusb/1.0.9/lib/pkgconfig/libusb-1.0.pc
/usr/local/Cellar/libusb/1.0.9/lib/ (2 other files)
anything:usb mymac$

GCC attempts (all failed):

gcc -o xout usbtest.c
gcc -o xout usbtest.c -lusb-1.0
gcc -L/usr/local/Cellar/libusb/1.0.9/lib -o xout usbtest.c -lusb-1.0

Error for all attempts:

usbtest.c:3:10: fatal error: 'libusb.h' file not found
#include <libusb.h>

Code:

#include <stdio.h>
#include <stdlib.h>
#include <libusb.h>

int main(int argc, const char * argv[])
{
    libusb_device **devs;
    libusb_context *context = NULL;

    size_t list;
    //size_t i;
    int ret;

    ret = libusb_init(&context);

    if(ret < 0)
    {
        perror("libusb_init");
        exit(1);
    }

    list = libusb_get_device_list(context, &devs);

    printf("There are %zd devices found\n", list);

    return 0;
}

Answer 1

You are not telling gcc where to look for the header files. This is done by the -I option on the gcc command line for compiling.

e.g.

gcc -I /usr/local/include -o xout usbtest.c

I think Homebrew does provide a symbolic link frominside the Cellar to /usr/local

Answer 2

So I had a similar issue, for some reason gcc doesnt include /usr/local/lib in its default search path on OS X. The quick fix is to add:

-lusb-1.0

to the gcc commands and it should compile.