1 files changed, 82 insertions, 0 deletions
diff --git a/dns.c b/dns.c
new file mode 100644
index 0000000..68f94bd
--- /dev/null
+++ b/dns.c
@@ -0,0 +1,82 @@
+/*
+ *	Copyright (c) 1999-2003 Smithsonian Astrophysical Observatory
+ */
+
+#include <unistd.h>
+#include <strings.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <netdb.h>              /* gethostbyname() */
+#include <arpa/inet.h>
+
+#define SZ_LINE 1024
+
+int main(int argc, char **argv)
+{
+  int i, got;
+  char host[SZ_LINE];
+  struct hostent *hostent;
+  struct addrinfo *hints=NULL, *addrinfo=NULL;
+  struct sockaddr_in * p;
+
+  // gethost
+  if( argc > 1 )
+    strcpy(host, argv[1]);
+  else{
+    fprintf(stderr, "calling gethostname() ...\n");
+    if( gethostname(host, SZ_LINE) == -1 ){
+      perror("gethostname");
+      exit(1);
+    }
+    else{
+      fprintf(stderr, "host name is %s\n", host);
+    }
+  }
+  fprintf(stderr, "\n");
+
+  fprintf(stderr, "calling getaddrinfo (preferred) ...\n");
+  hints = (struct addrinfo *)calloc(1, sizeof(struct addrinfo));
+  hints->ai_flags |= AI_CANONNAME;
+  hints->ai_family = AF_INET;
+  got = getaddrinfo(host, NULL, hints, &addrinfo);
+  if( got != 0 ){
+    fprintf(stderr, "getaddrinfo rtn: %d %s\n", got, gai_strerror(got));
+    perror("getaddrinfo");
+    exit(1);
+  }
+  else{
+    fprintf(stderr, "getaddrinfo() succeeded\n");
+  }
+  fprintf(stderr, "printing ip address via getaddrinfo ...\n");
+  if( addrinfo ){
+    p = (struct sockaddr_in *)(addrinfo->ai_addr);
+    fprintf(stderr, "%x (canonical: %s)\n", p->sin_addr.s_addr, addrinfo->ai_canonname);
+    freeaddrinfo(addrinfo);
+    if( hints ) free(hints);
+  }
+  else{
+    fprintf(stderr, "ERROR: can't look up: %s\n", host);
+  }
+  fprintf(stderr, "\n");
+
+  fprintf(stderr, "calling gethostbyname (obsolete) ...\n");
+  if( !(hostent = gethostbyname(host)) ){
+      perror("gethostbyname");
+      exit(1);
+  }
+  else{
+    fprintf(stderr, "gethostbyname() succeeded\n");
+  }
+  fprintf(stderr, "printing ip address(es) via gethostbyname ...\n");
+  if( hostent ){
+    for(i=0; hostent->h_addr_list[i]; i++){
+      fprintf(stderr, "%x\n", *(int *)hostent->h_addr_list[i]);
+    }
+  }
+  else{
+    fprintf(stderr, "ERROR: can't look up: %s\n", host);
+  }
+  fprintf(stderr, "\n");
+
+  return(0);
+}