Data commit

Task/DNS-query/C/dns-query.c

@@ -0,0 +1,58 @@
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>		/* getaddrinfo, getnameinfo */
+#include <stdio.h>		/* fprintf, printf */
+#include <stdlib.h>		/* exit */
+#include <string.h>		/* memset */
+
+int
+main()
+{
+	struct addrinfo hints, *res, *res0;
+	int error;
+	char host[NI_MAXHOST];
+
+	/*
+	 * Request only one socket type from getaddrinfo(). Else we
+	 * would get both SOCK_DGRAM and SOCK_STREAM, and print two
+	 * copies of each numeric address.
+	 */
+	memset(&hints, 0, sizeof hints);
+	hints.ai_family = PF_UNSPEC;     /* IPv4, IPv6, or anything */
+	hints.ai_socktype = SOCK_DGRAM;  /* Dummy socket type */
+
+	/*
+	 * Use getaddrinfo() to resolve "www.kame.net" and allocate
+	 * a linked list of addresses.
+	 */
+	error = getaddrinfo("www.kame.net", NULL, &hints, &res0);
+	if (error) {
+		fprintf(stderr, "%s\n", gai_strerror(error));
+		exit(1);
+	}
+
+	/* Iterate the linked list. */
+	for (res = res0; res; res = res->ai_next) {
+		/*
+		 * Use getnameinfo() to convert res->ai_addr to a
+		 * printable string.
+		 *
+		 * NI_NUMERICHOST means to present the numeric address
+		 * without doing reverse DNS to get a domain name.
+		 */
+		error = getnameinfo(res->ai_addr, res->ai_addrlen,
+		    host, sizeof host, NULL, 0, NI_NUMERICHOST);
+
+		if (error) {
+			fprintf(stderr, "%s\n", gai_strerror(error));
+		} else {
+			/* Print the numeric address. */
+			printf("%s\n", host);
+		}
+	}
+
+	/* Free the linked list. */
+	freeaddrinfo(res0);
+
+	return 0;
+}