Get the domain name in linux (C programming)

Question

other than getdomainname() is there any way to get the domain name on Linux without having to open and parse files in /etc?

Code is appreciated.

Thanks

Answer 1

For future reference, Linux and some other systems have a getdomainname() function which should do what you want, although this is not part of the POSIX standard.

Answer 2

Try the following:

#include <string.h>
#include <netdb.h>
#include <unistd.h>
#include <stdio.h>

int main(int argc, char* argv[])
{
  char hn[254];
  char *dn;
  struct hostent *hp;

  gethostname(hn, 254);
  hp = gethostbyname(hn);
  dn = strchr(hp->h_name, '.');
  if ( dn != NULL ) {
    printf("%s\n", ++dn);
  }
  else {
    printf("No domain name available through gethostbyname().\n");
  }

  return 0;
}

It seems that getdomainname() will only tell you a NIS or YP domain name, which you probably won't have set. Querying for the full hostname with gethostbyname(), on the other hand, checks a variety of different sources (including DNS and /etc/hosts) to determine your canonical hostname.