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#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
int main(int argc, char** argv)
{
if (argc < 2) {
printf("usage: host <hostname>\n");
return 0;
}
// If input looks like an IPv4 address, we should do a reverse lookup.
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(53);
int rc = inet_pton(AF_INET, argv[1], &addr.sin_addr);
if (rc == 1) {
// Okay, let's do a reverse lookup.
auto* hostent = gethostbyaddr(&addr.sin_addr, sizeof(in_addr), AF_INET);
if (!hostent) {
fprintf(stderr, "Reverse lookup failed for '%s'\n", argv[1]);
return 1;
}
printf("%s is %s\n", argv[1], hostent->h_name);
return 0;
}
auto* hostent = gethostbyname(argv[1]);
if (!hostent) {
fprintf(stderr, "Lookup failed for '%s'\n", argv[1]);
return 1;
}
char buffer[32];
const char* ip_str = inet_ntop(AF_INET, hostent->h_addr_list[0], buffer, sizeof(buffer));
printf("%s is %s\n", argv[1], ip_str);
return 0;
}
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