[SOLVED] How would I do this...

Mouse750 · 09-16-2011, 02:50 PM

Please look at the following:

Code:

# network.txt
config interface lan
	option ifname	eth0.1
	option type	bridge
	option proto	static
	option ipaddr	192.168.1.1
	option netmask	255.255.255.0

config interface wan
	option ifname	eth1 #<- How do I grab this, store it as a var?
	option proto	dhcp

In this case I'm trying to grab eth1. It's not aways going to be eth1.

I was trying something like:

cat network.txt | grep "something"

If I try cat network.txt | grep "option ifname"

I get

Code:

	option ifname	lo
	option ifname	eth0.1
	option ifname	eth1

However, I only wanted the line that belonged to

Code:

config interface wan

which would be

Code:

option ifname	eth1

but then that's still too much info because I wanted the last word:

Code:

eth1

Then I want to take the answer (In this case eth1) and store it as X=(the answer)

Nominal Animal · 09-16-2011, 03:59 PM

Use awk:

Code:

awk '($1=="config" && $2=="interface") { active = ($3=="wan") }
     (active && $1=="option" && $2=="ifname") { print $3; ok=1; exit(0) }
     END { exit(1-ok) }' network.txt

When it sees the "config interface wan" line, it will set active to true.

When active is true, and it sees "option ifname", it will print the third field, set ok to 1, and exit (skip to the end rule).

At END, if ok has been set to 1, the value was printed, and the scriptlet returns exit status 0. Otherwise it will return exit status 1.

This means that in a Bourne shell, POSIX shell, or Bash script, you can use

Code:

if IFNAME=`awk '($1=="config" && $2=="interface") { active = ($3=="wan") }
                 (active && $1=="option" && $2=="ifname") { print $3; ok=1; exit(0) }
                 END { exit(1-ok) }' network.txt` ; then
        echo "WAN interface is up, $IFNAME"
else
        echo "WAN interface is down."
fi

Another possibility is to do the same thing in sed:

Code:

sed -ne '/^[\t ]*config[\t ]\+interface[\t ]\+wan[\t ]*$/,/^[\t ]*config[\t ]/ s|^[\t ]*option[\t ]\+ifname[\t ]\+\([^\t ]\+\).*$|\1|p' network.txt

although it will not return nonzero exit status when nothing is output.

DoomUs · 09-16-2011, 04:39 PM

Another solution.

I'm assuming you're using strictly utilities available in the terminal, i.e. bash commands, is that right?

If so, do you plan on writing a script to do this or what?

When you suggest storing your result as X=(the answer) are you referring to an environment variable called X?

Will Networking.txt always be the same?

This is NOT the cleanest or best way to do this, in fact, it can likely be done with one or two "awk" or "grep" or "sed" statements, I'm just not that good, so hacking though,
Here's my suggestion, hopefully it gets you in the right direction.

Code:

head -`echo 7 + $(cat -n network.txt | grep -r "config.*wan$" | awk -F " " '{print $1}') | bc` network.txt | tail -5 | grep "option ifname" | awk -F " " '{print $3}'

the explanation:

Code:

//(1) write out the network.txt file with line numbers and print the line that has "config" and ends with "wan" because that's the interface you're looking for
cat -n network.txt | grep -r "config.*wan$"

//(2)send (1) via pipe to this statement to get just the line number from that string
awk -F " " '{print $1}'

//(3) with (2), we now just have a line-number (let's suppose it was at line 8), which we pipe to "bc" to add with 7 from the echo the simplified code looks like this
//we want to add some lines to the number eight where we found the "config.*wan$" string because the option iface will be after that
echo 7 + 8 | bc
//this echo piped to bc produces the number 15.

//(4) with the number 15, we pass as an argument to "head", which will pull the first 15 lines of a file provided
head -15 network.txt

//(5) with the first 15 lines of network.txt, we don't need all of them, we really only need the ones concerning the "wan" interface, so we pipe to tail
//so we end up with the last 5 lines of the first 15 lines of network.txt
head -15 network.txt | tail -5

//(6) we pipe this to grep for the "option iface" you were actually looking for
head -15 network.txt | tail -5 | grep "option ifname"

//(7) now we have the line we want "option ifname eth1" which we can cut up with awk to get the 3rd "element" of
head -15 network.txt | tail -5 | grep "option ifname" | awk -F " " '{print $3}'

//(8) we're all done, and it prints
eth1

//(9) set it to a variable
a=$(head -`echo 7 + $(cat -n network.txt | grep -r "config.*wan$" | awk -F " " '{print $1}') | bc` network.txt | tail -5 | grep "option ifname" | awk -F " " '{print $3}')

Mouse750 · 09-16-2011, 08:09 PM

Thank You!!!

This is the reason I was asking:

Code:

#!/bin/sh                                                                 
                                                                          
if IFNAME=`awk '($1=="config" && $2=="interface") { active = ($3=="wan") }
(active && $1=="option" && $2=="ifname") { print $3; ok=1; exit(0) }
END { exit(1-ok) }' /etc/config/network` ; then       

        iptables -R zone_wan_ACCEPT 1 -j ACCEPT -p tcp --destination-port 443 -o $IFNAME
else
        echo "iface not found in network, iptable rule not set"
fi

Your code works perfect but I forget to mention that sometimes the network.txt is formated like so:

Code:

config 'interface' 'lan'
	option 'ifname'		'eth0.1'
	option 'type'		'bridge'
	option 'proto'		'static'
	option 'ipaddr'		'192.168.1.1'
	option 'netmask'	'255.255.255.0'

config 'interface' 'wan'
	option 'ifname'		'eth1'
	option 'proto'		'dhcp'

How did you get so good at awk and sed? I'm just taking online shell tutorials but dream of getting as good as you.

ta0kira · 09-16-2011, 10:12 PM

A sed alternative:

Code:

sed -r '/config interface wan/,/config/{/ifname[\t ]/{s/.*ifname[\t ]+([^ ]*).*/\1/;q}};d' network.txt

Kevin Barry

Mouse750 · 09-16-2011, 10:47 PM

@ta0kira,

How do I use your example?

Code:

root@router:/etc/config# sed -r '/config interface wan/,/config/{/ifname /{s/.*ifname +([^ ]+)/\1/;p}};d' network.txt
root@router:/etc/config# sed -r '/config interface wan/,/config/{/ifname /{s/.*ifname +([^ ]+)/\1/;p}};d' network.txt
root@router:/etc/config# sed -r '/config interface wan/,/config/{/ifname /{s/.*ifname +([^ ]+)/\1/;p}};d' network.txt
root@router:/etc/config#

I keep running it but nothing happens?

ta0kira · 09-16-2011, 11:18 PM

Quote:

Originally Posted by Mouse750

@ta0kira,

How do I use your example?

Code:

root@router:/etc/config# sed -r '/config interface wan/,/config/{/ifname /{s/.*ifname +([^ ]+)/\1/;p}};d' network.txt
root@router:/etc/config# sed -r '/config interface wan/,/config/{/ifname /{s/.*ifname +([^ ]+)/\1/;p}};d' network.txt
root@router:/etc/config# sed -r '/config interface wan/,/config/{/ifname /{s/.*ifname +([^ ]+)/\1/;p}};d' network.txt
root@router:/etc/config#

I keep running it but nothing happens?

That version didn't allow for tabs, which I fixed shortly after I posted it (the tabs copied as spaces from the forum page). Please see my post again for a better version.
Kevin Barry

Mouse750 · 09-17-2011, 04:14 AM

Quote:

Originally Posted by ta0kira

That version didn't allow for tabs, which I fixed shortly after I posted it (the tabs copied as spaces from the forum page). Please see my post again for a better version.
Kevin Barry

Kevin, Would it be possible to make the code also work for:

Code:

#network.txt
config 'interface' 'lan'
	option 'ifname'		'eth0.1'
	option 'type'		'bridge'
	option 'proto'		'static'
	option 'ipaddr'		'192.168.1.1'
	option 'netmask'	'255.255.255.0'

config 'interface' 'wan'
	option 'ifname'		'eth1'
	option 'proto'		'dhcp'

Aslo, how do I store sed's output to a var?

Nylex · 09-17-2011, 04:23 AM

Quote:

Originally Posted by Mouse750

Aslo, how do I store sed's output to a var?

If you're using Bash, see this (the bottom of that page is what you want). The Advanced Bash Scripting Guide is pretty good in general.

Mouse750 · 09-17-2011, 04:34 AM

Thanks, Nylex

I was trying IFACE=$(( sed foo bar )) but after reading your link It was IFACE=$(sed foo bar)

Now if I could only get that code to also work for:

Code:

#network.txt
config 'interface' 'lan'
	option 'ifname'		'eth0.1'
	option 'type'		'bridge'
	option 'proto'		'static'
	option 'ipaddr'		'192.168.1.1'
	option 'netmask'	'255.255.255.0'

config 'interface' 'wan'
	option 'ifname'		'eth1'
	option 'proto'		'dhcp'

After this, I'm going to try my best to learn sed and awk, any tutorial links welcome.

grail · 09-17-2011, 07:00 AM

Well I am not sure why this needs to be so hard:

Code:

IFACE=$(awk '/wan/{getline;gsub(/\047/,"");print $NF}') network.txt

IFACE=$(sed -nr "/wan/{n;s/'//g;s/.*[[:space:]]+(.+)/\1/p}") network.txt

IFACE=$(ruby -ane "puts readline.scan(/.+[[:space:]]'?([^']+)'?/)[0] if /wan/") network.txt

ta0kira · 09-17-2011, 07:09 AM

Quote:

Originally Posted by Mouse750

Kevin, Would it be possible to make the code also work for:

Code:

#network.txt
config 'interface' 'lan'
	option 'ifname'		'eth0.1'
	option 'type'		'bridge'
	option 'proto'		'static'
	option 'ipaddr'		'192.168.1.1'
	option 'netmask'	'255.255.255.0'

config 'interface' 'wan'
	option 'ifname'		'eth1'
	option 'proto'		'dhcp'

Aslo, how do I store sed's output to a var?

Code:

IFACE="$( sed -r "s/'//g;"'s/[\t ]+/ /g;/config interface wan/,/config/{/ifname /{s/.*ifname ([^ ]*).*/\1/;q}};d' network.txt )"

I also made a few changes that just clean it up a little.
Kevin Barry

Nylex · 09-17-2011, 07:14 AM

Quote:

Originally Posted by Mouse750

After this, I'm going to try my best to learn sed and awk, any tutorial links welcome.

Have a look at http://www.grymoire.com/Unix/.

Mouse750 · 09-17-2011, 09:55 AM

Thanks You!!

TaOkira, your code works great on both. Is there any way possible you could explain your code in such a way that a complete amateur such as myself could at least understand some of it?. I try using sed for simple things but I get stuck when I run into special characters.

grail, I could not get your awk or sed code to work. I was just getting a flashing prompt. I don't know what I was doing wrong.

grail · 09-17-2011, 10:33 AM

Strange ... you didn't by chance change any of the quotes?