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Full Discussion: gethostbyname_r returns NULL when hostname has dash
Special Forums IP Networking gethostbyname_r returns NULL when hostname has dash Post 302197755 by uunniixx on Wednesday 21st of May 2008 03:24:42 PM
Old 05-21-2008
Below are my personal findings:


Example 1:

Code:
> host nyustern-.collegemailer.com
nyustern-.collegemailer.com has address 209.200.118.155

> host nyustern.collegemailer.com
nyustern.collegemailer.com has address 209.200.118.155

Example 2:

Code:
> nslookup nyustern-.collegemailer.com
Note:  nslookup is deprecated and may be removed from future releases.
Consider using the `dig' or `host' programs instead.  Run nslookup with
the `-sil[ent]' option to prevent this message from appearing.
Server:         xx.xxx.xx.xxx
Address:       xx.xxx.xx.xxx#xx
 
Non-authoritative answer:
Name:   nyustern-.collegemailer.com
Address: 209.200.118.155
 
> nslookup nyustern.collegemailer.com
Note:  nslookup is deprecated and may be removed from future releases.
Consider using the `dig' or `host' programs instead.  Run nslookup with
the `-sil[ent]' option to prevent this message from appearing.
Server:         xx.xxx.xx.xxx
Address:       xx.xxx.xx.xxx#xx
 
Non-authoritative answer:
Name:   nyustern.collegemailer.com
Address: 209.200.118.155

Example 3:

This code uses gethostbyname_r method to determine the address:-

Code:
> a.out nyuster-n.collegemailer.com
addresses:   209.200.118.155
> a.out ny-uster-n.collegemailer.com
addresses:   209.200.118.155
> a.out ny-uster-n-.collegemailer.com
unknown host `ny-uster-n-.collegemailer.com'
> a.out ny---uster-n.collegemailer.com
addresses:   209.200.118.155
> a.out nyustern.collegemailer.com
addresses:   209.200.118.155
>

I am unsure whether '-' in hostname ignored or does not has a functionality. In such a case having a trailing '-' is just a corner off case.
Last edited by uunniixx; 05-25-2008 at 06:16 PM..
 

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LEARN ABOUT MINIX

hosts

HOSTS(5)							File Formats Manual							  HOSTS(5)

NAME

       hosts - hostname to IP address database

SYNOPSIS

       /etc/hosts

DESCRIPTION

       The  hosts  database  lists the IP addresses and the hostnames that translate to these IP addresses.  It is used by nonamed(8) in a network
       without name servers.  A simple /etc/hosts may look like this:

	      127.0.0.1      localhost
	      192.9.200.1    darask
	      192.9.200.2    burask

       The localhost entry lists a special address that refers to the local host itself (a kind of /dev/tty for hosts.)  You should only  list	it
       if nonamed needs it!  The other entries are actual machines.  The file may contain comments marked with '#'.

       You  can  have  aliases	(more  hostnames on the same line), but it is not recommended, because nonamed can't present them to the system as
       CNAME records.  An often seen form like

	      192.9.200.1    darask.home.cs.vu.nl  darask

       is harmless though, and has the small advantage that you can use the short name in /etc/ethers so rarpd can match it at boot time.

FILES

       /etc/hosts     Hosts database.

SEE ALSO

       ethers(5), nonamed(8), rarpd(8), boot(8).

AUTHOR

       Kees J. Bot (kjb@cs.vu.nl)

																	  HOSTS(5)
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