因开发需要获取有线网卡的MAC地址，发现网上获取的方法多数只能获取联网网卡的MAC地址，因此重写了下Ubuntu 10下测试通过。 下面代码无论网卡是否连线，都可以获取MAC地址，稍作修改，可以输出系统所有的网卡硬件MAC地址，无论是否已经联网。

getmac.c

/* 
 * getmac.c 
 * 
 *  Created on: 2010-11-4 
 *      Author: carl 
 */ 

#include <stdio.h> 
#include <fcntl.h> 
#include <stdlib.h> 
#include <string.h> 
#include <unistd.h> 

#include <sys/ioctl.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <linux/if.h> 

#define IFNAMSIZ 16 

// data structs to store interface name list 
char ifname_buf[2048]; 
char *ifnames = ifname_buf; 
int count = 0; 

void add_interface_name(const char * name) 
{ 
    int i; 
    for (i=0;i<count;i++) 
    { 
        if (!strcmp(ifnames+i*IFNAMSIZ, name)) 
            return; 
    } 
    strncpy(ifnames+(count++)*IFNAMSIZ, name, IFNAMSIZ-1); 
} 

char * get_name(char *name, char *p) 
{ 
    while (isspace(*p)) 
    p++; 
    while (*p) { 
    if (isspace(*p)) 
        break; 
    if (*p == ':') {    /* could be an alias */ 
        char *dot = p, *dotname = name; 
        *name++ = *p++; 
        while (isdigit(*p)) 
        *name++ = *p++; 
        if (*p != ':') {    /* it wasn't, backup */ 
        p = dot; 
        name = dotname; 
        } 
        if (*p == '\0') 
        return NULL; 
        p++; 
        break; 
    } 
    *name++ = *p++; 
    } 
    *name++ = '\0'; 
    return p; 
} 

// get /proc/net/dev interface name list into buffer 
// return 0 if success 
int get_procnet_list() 
{ 
    FILE *fh; 
    char buf[512]; 
    fh = fopen("/proc/net/dev", "r"); 
    if (!fh) 
        return -1; 

    fgets(buf, sizeof buf, fh); /* eat title lines */ 
    fgets(buf, sizeof buf, fh); 
    while (fgets(buf, sizeof buf, fh)) 
    { 
        char name[IFNAMSIZ]; 
        get_name(name, buf); 
        add_interface_name(name); 
    } 
    fclose(fh); 
    return 0; 
} 

long mac_addr_sys ( u_char *addr) 
{ 
/* implementation for Linux */ 
    struct ifreq ifr; 
    struct ifreq *IFR; 
    struct ifconf ifc; 
    char buf[1024]; 
    int s, i; 
    int ok = 0; 

    // clear buffer 
    memset(ifname_buf, 0, sizeof(ifname_buf)); 

    s = socket(AF_INET, SOCK_DGRAM, 0); 
    if (s==-1) { 
        return -1; 
    } 

    ifc.ifc_len = sizeof(buf); 
    ifc.ifc_buf = buf; 
    ioctl(s, SIOCGIFCONF, &ifc); 

    IFR = ifc.ifc_req; 
    // put the ioctl interface names in the list 
    for (i = ifc.ifc_len / sizeof(struct ifreq); --i >= 0; IFR++) { 
            add_interface_name(IFR->ifr_name); 
    } 
    // put the /proc/net/dev interface names in the list 
    if (get_procnet_list()) 
        return -1; 

    // get the first mac address of eth* device hardware address 
    for (i = 0; i < count; i++) { 
        strcpy(ifr.ifr_name, ifnames + i*IFNAMSIZ); 
        if (!strncmp(ifr.ifr_name, "eth", 3)) 
            if (ioctl(s, SIOCGIFFLAGS, &ifr) == 0) { 
                if (! (ifr.ifr_flags & IFF_LOOPBACK)) { 
                    if (ioctl(s, SIOCGIFHWADDR, &ifr) == 0) { 
                        char *p = (char *)ifr.ifr_hwaddr.sa_data; 
                        if (!*((int *)p) && !*((int *)(p+2)) ) 
                            continue; 
                        // if not 00:00:00:00:00:00, yes, we get the real mac addr 
                        ok = 1; 
                        break; 
                    } 
                } 
            } 
    } 

    close(s); 
    if (ok) { 
        bcopy( ifr.ifr_hwaddr.sa_data, addr, 6); 
    } 
    else { 
        return -1; 
    } 
    return 0; 
} 

/***********************************************************************/ 
/* 
 * Main (only for testing) 
 */ 
int main( int argc, char **argv) 
{ 
    long stat; 
    int i; 
    u_char addr[6]; 

    stat = mac_addr_sys( addr); 
    if (0 == stat) { 
        printf( "MAC address = "); 
        for (i=0; i<6; ++i) { 
            printf("%2.2x", addr[i]); 
            if (i<5) 
                printf(":"); 
        } 
        printf( "\n"); 
    } 
    else { 
        fprintf( stderr, "can't get MAC address\n"); 
        exit( 1); 
    } 
    return 0; 
}