simple/dns/gethostbyaddr.c

58 lines
1.1 KiB
C

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include "hstrerror.h"
char *cmnd;
void usage(void) {
fprintf(stderr, "Usage: %s [hostname ...]\n", cmnd);
exit(1);
}
int main(int argc, char **argv) {
int i;
int rc = 0;
cmnd = argv[0];
if (argc < 2) {
usage();
}
for (i = 1; i < argc; i++) {
struct in_addr ia;
if (!inet_aton(argv[i], &ia)) {
fprintf(stderr, "%s: cannot parse %s\n",
argv[0], argv[i]);
continue;
}
struct hostent *he = gethostbyaddr(&ia, sizeof(ia), AF_INET);
char **a;
if (!he) {
fprintf(stderr, "%s: cannot resolve %s: %s\n",
argv[0], argv[i], hstrerror(h_errno));
rc++;
continue;
}
printf("%s\n", argv[i]);
printf("\tCanonical: %s\n", he->h_name);
for (a = he->h_aliases; *a; a++) {
printf("\tAlias: %s\n", *a);
}
for (a = he->h_addr_list; *a; a++) {
int j;
printf("\tAddress: ");
for (j = 0; j < he->h_length; j++) {
printf("%s%d", j ? "." : "", (unsigned char)(*a)[j]);
}
printf("\n");
}
printf("\n");
}
return rc;
}