Subject: Re: Why is ifconfig.ae0 better than hostname.ae0?
To: Andrew Brown <>
From: Luke Mewburn <>
List: tech-net
Date: 04/16/1997 23:25:33
Andrew Brown writes:
> >> >Parsing begins to become a serious pain.
> >> 
> >> are inet addresses no longer going to be assigned this way?  isn't
> >> netstart supposed to be able to read the ifconfig.### files anyway?
> >> doens't it "implicitly" know how to parse the file?
> >
> > works by having netstart do "ifconfig foo `cat`"
> >That isn't parsing by any normal use of the term.
> wow.  i guess it's been too long since i looked at netstart.  yes,
> you are correct.  it doesn't even pretend to know what's in them
> anymore.  hmm...

Parsing the format of either /etc/ifconfig.xxN or $ifconfig_xxN is
to get the interface address is too much work.

A proposed solution is as follows:
	a) add an option to ifconfig(8) which returns the inet source
	   address for a given interface.
	b) modify /etc/netstart to take advantage of this

a) I've done this. It was rather simple, in the end. I just added a
'-q' (``quiet'') option. Currently, it's only effective if you do
something like
	ifconfig -q ed0
and it will return a string like "" if things are OK, or
an null string if no address is bound to the interface. If there's a
problem, the message goes to STDERR and a non-zero exit status is

b) Replace the code in /etc/netstart that looks like (well, similar
to; i'm just getting the gist across here):

	for i in `list of interfaces` ; do 
		if [$ifconfig_$$tmp != ""]; then	# (you get the idea)
			ifconfig $i $ifconfig_$$tmp
		elif [-f /etc/ifconfig.$i]; then
			ifconfig `cat /etc/ifconfig.$i`
			echo "can't configure $i"
			# <-------------------------- point `A'
		# <---------------------------------- point `B'
	route add `hostname` localhost	# <---------- point `C'

Point `A': Add a "continue"

Point `B': Add something like:
	$addr=`ifconfig -q $i`
	if [$addr != ""]; then
		route add $addr localhost

Point `C': remove the line

I'll test this latter code, but I'm pretty sure that this is a sane
solution. The "ifconfig -q ..." bit may be a bit hacky for some,