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gcc system call to get gateway address?

Posted on 1998-12-09
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Last Modified: 2008-02-01
We are using  gethostname() and getdomainname() that are
part of gcc with our Red Hat Linux 5.1 installation.  We
would like to find a  get gateway address  function.  What
system function can we call to get  gateway address?
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Question by:amw23
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by:elfie
ID: 1254973
Do you know the name of gateway system?
If not try experimenting with 'ping', and try find out the routing of a package. Lookfor a change in the addresses you receive from ping.
(use ping in verbose mode/show systems/...)
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mlonnrot earned 50 total points
ID: 1254974
There is no system call for this. I also don't think there's a portable way of doing it. Use popen() to run a UNIX command that returns the default router. For example:

f1 = popen("netstat -r | awk '/^default/{print $2}', "r");
fgets(defRoute, sizeof(defRoute)-1, f1)

Problem with this approach is that netstat truncates long hostnames, so you may end up with garbage. Most systems include options for the route command, i.e. "route get default". Put that in the popen() but you need root privs to run it.
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