#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <strings.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <time.h>


/* compile: cc -o checkname checkname.c 
 *
 * usage: 
 *    unix% checkname
 * Will print the local host name as best as can be determined.
 */


char *GetFQDN(void)
{
  char buff[BUFSIZ];
  static char *retval;
  struct hostent	*hp;
  char		*p;
  char		**ap;
  char *domain;

  /* Return any old results. */
  if (retval)
    return retval;

  /* Try gethostname. */
  bzero(buff,BUFSIZ);
  if (gethostname(buff, BUFSIZ) < 0) {
    printf("Error calling gethostname!  This should not happen\n");
    return NULL;
  }
  if (strchr(buff, '.') != NULL) {
    retval=strdup(buff);
    return retval;
  }

  /* See if DNS (or /etc/hosts) gives us a full domain name. */
  if ((hp = gethostbyname(buff)) != NULL) {
    /* First, see if the main name is a FQDN.  It should be. */
    if (hp != NULL && 
	strchr(hp->h_name, '.') != NULL && 
	strstr(hp->h_name,"localdomain")==0 ) {
      if (strlen(hp->h_name) < BUFSIZ - 1) {
	return strcpy(buff, hp->h_name);
      }
      /* Doesn't fit; make sure we don't return bad data next time. */
      buff[0] = '\0';
      printf("Host name too long.\n");
      retval=NULL;
      return hp->h_name;
    }
    
    /* Second, see if any aliases are. */
    if ((ap = hp->h_aliases) != NULL) {
      while ((p = *ap++) != NULL) {
	if (strchr(p, '.') != NULL &&
	    strstr(p,"localdomain")==0 ) {
	  retval=strdup(p);
	  return retval;
	}
      }
    }
  } 

  /* Give up:  Get SP_DOMAIN and append it. */
  printf("The gethostbyname call returned either no domain, or 'localdomain'\n"
	 "Neither of these will work, falling back to $SP_DOMAIN.\n");
  if (!(domain=getenv("SP_DOMAIN"))) {
    printf("SP_DOMAIN not set!\n");
    return NULL;
  }
  /* restore base hostname */
  bzero(buff,BUFSIZ);
  if (gethostname(buff, BUFSIZ) < 0) /* this already worked once */
    return NULL;
  (void)strcat(buff, ".");
  (void)strcat(buff, domain);
  retval=strdup(buff);
  return retval;
}

main()
{
  char *host;
  if (!(host=GetFQDN())) {
    printf("\
Couldn't get any local host information.  This may mean that your\n\
computer is not configured properly.  You may need to add the host\n\
name to /etc/hosts.   See the man page for gethostbyname.\n");
    return 0;
  }

  if (!getenv("SP_DOMAIN")) {
    printf("\
Note: the $SP_DOMAIN variable is not set.\n\
If gethostname (or this program) doesn't return any domain information,\n\
this variable needs to be set (normally in $SPOCK/Spockrc).\n\
\n\
For the purposes if this test program, set it in the shell if you need it.\n");
  }

  printf("\nThe local host name for this machine is %s\n",host);
}