gethostbyname示例

#include <netdb.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
 
const int inet_addrstrlen=16;
 
int main(int argc, char **argv) {
    char *ptr, **pptr;
    char str[inet_addrstrlen];
    struct hostent *hptr;
 
    while(--argc>0) {
        ptr=*++argv;
        if((hptr=gethostbyname(ptr)) == NULL) {
            fprintf(stderr, "gethostbyname error for host: %s: %s\n", ptr, hstrerror(h_errno));
            continue;
        }
        printf("official hostname: %s\n", hptr->h_name);
 
        for(pptr=hptr->h_aliases; *pptr!=NULL; pptr++) {
            printf("\talias: %s\n", *pptr);
        }
 
        switch(hptr->h_addrtype) {
        case AF_INET:
            pptr=hptr->h_addr_list;
            for(;*pptr!=NULL;pptr++) {
                printf("\taddress: %s\n", inet_ntop(hptr->h_addrtype, *pptr, str, sizeof(str)));
            }
            break;
        default:
            fprintf(stderr, "unknown address type\n");
            break;
        }
    }
    exit(0);
}