How to get network adapter stats in linux/Mac OSX?

I'm looking for a way to get hold of network stats in C on Linux and MacOSX. Specifically, I need to monitor the number of bytes uploaded and downloaded from each network adapter on the system - I don't need to do packet inspection, or differentiate between protocols, just a 'total bytes' counter which I can poll at intervals would be fine. In Windows I can do this using the iphlpapi.dll library via GetIfTable (to list the network adapters) and GetIfEntry (to read the stats), but I can't find the Linux/OSX equivalents. My knowledge of C is fairly basic so I would appreciate a solution that isn't too involved. Any help would be much appreciated!

The Darwin netstat source code uses sysctl. Here's some code that prints the number of bytes in and out on OSX:

#import <Foundation/Foundation.h>
#include <sys/sysctl.h>
#include <netinet/in.h>
#include <net/if.h>
#include <net/route.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    int mib[] = {
        CTL_NET,
        PF_ROUTE,
        0,
        0,
        NET_RT_IFLIST2,
        0
    };
    size_t len;
    if (sysctl(mib, 6, NULL, &len, NULL, 0) < 0) {
        fprintf(stderr, "sysctl: %s\n", strerror(errno));
        exit(1);
    }
    char *buf = (char *)malloc(len);
    if (sysctl(mib, 6, buf, &len, NULL, 0) < 0) {
        fprintf(stderr, "sysctl: %s\n", strerror(errno));
        exit(1);
    }
    char *lim = buf + len;
    char *next = NULL;
    u_int64_t totalibytes = 0;
    u_int64_t totalobytes = 0;
    for (next = buf; next < lim; ) {
        struct if_msghdr *ifm = (struct if_msghdr *)next;
        next += ifm->ifm_msglen;
        if (ifm->ifm_type == RTM_IFINFO2) {
            struct if_msghdr2 *if2m = (struct if_msghdr2 *)ifm;
            totalibytes += if2m->ifm_data.ifi_ibytes;
            totalobytes += if2m->ifm_data.ifi_obytes;
        }
    }
    printf("total ibytes %qu\tobytes %qu\n", totalibytes, totalobytes);
    [pool drain];
    return 0;
}

I can't speak to OSX but on linux take a look at /proc/net/dev.

If you do 'cat /proc/net/dev' you should see statistics including 'bytes' - the total number of bytes of data transmitted or received by the interface. You can read the file within your own program.

EDIT:

I didn't read your whole question. This article should help you get started with /proc and has a section on /proc/net/dev.

Also, to list the interfaces you can call ioctl with the SIOCGIFCONF option. You can Google for a decent code example on how to loop through the returned data. Or you can simply pull it out of the /proc.net/dev data mentioned above, which should be easier.

on Linux:

• low level: check /sys/class/net/eth0/statistics/
• slightly higher level: ip -s link show eth0
• graphical: iftop
• interactive: iptraf