자신의 PC의 IP를 알아내야 하는 상황인데...

간단하게 만들어 본 것입니다...

#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/utsname.h>

char **my_addrs(int *addrtype);

int main() {

        char **pptr;
        char str[16];
        int addrtype;

        if((pptr = my_addrs(&addrtype)) == NULL) {
                printf("my_addrs error\n");
                exit(0);
        }

        for( ; *pptr != NULL; pptr++) {
                printf("my address: %s\n", inet_ntop(addrtype, *pptr, str, sizeof(str)));
        }

        return 0;
}

char **my_addrs(int *addrtype) {
        struct hostent *hptr;
        struct utsname myname;

        if(uname(&myname) < 0)
                return NULL;

        if((hptr = gethostbyname(myname.nodename)) == NULL)
                return NULL;

        *addrtype = hptr->h_addrtype;

        return hptr->h_addr_list;
}

그럼, ioctl함수에 SIOCGIFCONF request를 줘서 해결해 보세요.

# 추가: 예전에 kldp 어딘가에서 봤던 소스입니다.

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <ctype.h> 
#include <sys/types.h> 
#include <sys/ioctl.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <arpa/inet.h> 
#include <stropts.h> 

#if defined(sun) 
#include <sys/sockio.h> 
#endif 

#include <net/if.h> 
#if defined(linux) 
#include <linux/sockios.h> 
#endif 

#define BUFFERSIZE 1024 
const char * localip = "0.0.0.0"; 

const char * myip(){ 
        const int MAX_NIC = 10; 
        struct ifconf ifc; 
        struct ifreq ifr[MAX_NIC]; 

        int s; 
        int nNumIFs; 
        int i; 
        int count; 
        int max=2; 
        static char ip[BUFFERSIZE]; 
        int cmd = SIOCGIFCONF; 

        max++; 

        ifc.ifc_len = sizeof ifr; 
        ifc.ifc_ifcu.ifcu_req = ifr; 

        if((s = socket(AF_INET,SOCK_STREAM,0)) < 0) { 
                perror("socket"); 
                exit(1); 
        } 

#if defined(_AIX) 
        cmd = CSIOCGIFCONF; 
#endif 

        if((s = ioctl(s, cmd, &ifc)) < 0) { 
                perror("ioctl"); 
                exit(1); 
        } 

        nNumIFs = ifc.ifc_len / sizeof (struct ifreq); 
        count = 0; 
        strcpy(ip, localip); 
        for(i = 0; i < nNumIFs; i++) { 
                struct in_addr addr; 
                if(ifc.ifc_ifcu.ifcu_req[i].ifr_ifru.ifru_addr.sa_family != AF_INET) { 
                        continue; 
                } 

                addr = ((struct sockaddr_in *) & ifc.ifc_ifcu.ifcu_req[i].ifr_ifru.ifru_addr)->sin_addr; 
                if(addr.s_addr == htonl(0x7f000001)) { 
                        continue; 
                } 
                strcpy(ip, inet_ntoa(addr)); 
                printf("%s IP: %s\n", ifc.ifc_ifcu.ifcu_req[i].ifr_ifrn.ifrn_name, ip); 
        } 
        return ip; 
} 

int main() { 
        printf("One of my IP is %s\n", myip()); 
        return 0; 
}