my lame attempt at a shell script...

Eric F Crist ecrist at
Mon Jan 3 20:23:03 PST 2005

On Jan 3, 2005, at 8:21 PM, Timothy Luoma wrote:

> On Jan 3, 2005, at 6:28 PM, Eric F Crist wrote:
>> A couple more questions, then I'm done. Promise.
>> I need to verify whether or not there is an entry for 
>> grog_firewall_oif
>> and grog_firewall_iif in /etc/rc.conf.  If not, I want to exit with an
>> error.
> You want to check for either "grog_firewall_oif" or 
> "grog_firewall_iif" in /etc/rc.conf
> egrep -v "^#" /etc/rc.conf |\
> egrep -q "grog_firewall_oif | grog_firewall_iif" || (echo "$0" ; exit 
> 1)
> The first line says "skips the comment lines" (the ones that begin 
> with #)

What does the second line do?  I tried, apparently, to accomplish the 
thing with some different syntax, yet unsuccessfully.

>> Also, a little more advanced, I need to pull information from an
>> ifconfig output.  I need to pull network numbers for both the internal
>> interface, as well as external interface.  For example,
>>          inet netmask 0xffffff00 broadcast
>>          inet6 fe80::20e:a6ff:feb9:2d3d%vr0 prefixlen 64 scopeid 0x3
>>          ether 00:0e:a6:b9:2d:3d
>>          media: Ethernet autoselect (100baseTX <full-duplex>)
>>          status: active
>> I don't actually need my own address, I need to be able to figure out
>> that the system, based on the above output, is on the
>> network.  This will be input into my firewall rulesets.
>> I imagine that there's a util or command around that can do this, or I
>> can code out the math, but there's got to be an easier way.
> How much can you assume?  Will you know the interface?  If so it's 
> fairly easy
> ifconfig vr0  |\
> 	tr '\012' ' ' |\
> 	 sed 's#.*inet ##; s# netmask.*##'
> roughly translated:
> line 1: give me the information for vr0 only
> line 2: replace the end of line (\012) and replace them with a space
> line 3: delete everything from the beginning of the line up to "inet " 
> and then delete everything from " netmask" to the end of the line
> Put it into a variable
> MY_IP=`ifconfig vr0  |\
> 	tr '\012' ' ' |\
> 	 sed 's#.*inet ##; s# netmask.*##'`
> TjL

I can assume everything, since grog_firewall_oif *should* be a value 
such as above.  On my system, grog_firewall_oif will be ath0.  This 
isn't assumed, but rather defined for me.  I would write the above line 
as follows (please verify syntax):

ifconfig $grog_firewall_oif |\
	tr '\012' ' ' |\
	sed 's#.*inet ##; s# netmask.*##'

oif_ip=`ifconfig $grog_firewall_oif |\
	tr '\012' ' ' |\
	sed 's#.*inet ##; s# netmask.*##'`

This is a lot of help, however, if you read:

>> I don't actually need my own address, I need to be able to figure out
>> that the system, based on the above output, is on the
>> network.

I need my NETWORK address, in this case (with netmask), 
which would be

Eric F Crist                  "I am so smart, S.M.R.T!"
Secure Computing Networks              -Homer J Simpson
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