Get the domain name in linux (C programming)

other than getdomainname() is there any way to get the domain name开发者_Go百科 on Linux without having to open and parse files in /etc?

Code is appreciated.

Thanks

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.

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.

#include <stdio.h>
#include <netdb.h>
#include <sys/socket.h>
#include <arpa/inet.h>
int main(int argc, char *argv[])
{
    int i;
    struct hostent *he;
    struct in_addr **addr_list;
    if (argc != 2) {
        fprintf(stderr,"usage: ghbn hostname\n");
        return 1;
    }
    if ((he = gethostbyname(argv[1])) == NULL) {
        herror("gethostbyname");
        return 2;
    }
    printf("domain name is: %s\n", he->h_name);
    printf("    IP addresses: ");
    addr_list = (struct in_addr **)he->h_addr_list;
    for(i = 0; addr_list[i] != NULL; i++) {
        printf("%s ", inet_ntoa(*addr_list[i]));
    }
    printf("\n");
    return 0;
}

run command:

gcc -o test test.c
./test www.google.com

Output:
domain name is: google.com
IP addresses: 172.217.163.110