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Newline in my script-built shell variable


 
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# 1  
Newline in my script-built shell variable

Hi all,

I'm not exactly a shell script guru, so this is probably a very silly question and I'm not seeing the point, but you know, sometimes it happens...

I have this script which adds entries to local arp cache using it to find the corresponding IP address.

Code:
# export MAC=00:25:90:34:3d:f2
# export IP=$(fping -c1 -g -q `ifconfig eth0 | grep "inet addr" | awk -F : {'print $2'} | awk {'print $1'} | awk -F . {'print $1"."$2"."$3".0/24"'}` &>/dev/null; echo  && arp -n | grep $MAC | awk {'print $1'})

The problem is that in every macro I use from now on, the variable $IP inserts a newline before being printed or used.

Code:
# echo "IP is $IP"
> IP is
> 192.168.26.59

I cannot use this variable inside a more complex command because of this newline.

Why is this happening and how to solve it?

I thank you all in advance.

Bye,
M.

Last edited by pludi; 06-03-2011 at 02:27 PM..
# 2  
Slide the trailing quote left of the variable, and the lf is just white space, poof.
Code:
# echo "IP is "$IP

# 3  
Quote:
Originally Posted by micantox
... the variable $IP inserts a newline before being printed or used.

...<snip>...

Why is this happening
After a brief glance at your code, I'd say the echo is to blame. If you don't need it, remove it. Or, you can do as DGPickett suggests and not quote the $IP.

Regards,
Alister
# 4  
Ok, I'm so sorry to have opened a thread for such a stupid question... I was totally sure to have tried every possible combination. Smilie

Ok, it was the last working day in the week and the last working hour in the day, but... Smilie

Thanks both of you!

M.
# 5  
I like my method of finding my local IP address better:
Code:
DEVICE="$(netstat -nr | sed -n '/^0.0/s/.* //p')"
test -z "$DEVICE"  &&  { echo "There is no default route"; exit 1; }
IP=$(/sbin/ifconfig $DEVICE 2>/dev/null | sed -n '/inet /s/.*addr:\([0-9.]*\).*/\1/p')

But if you want your external IP address or URL, there's a much more simple way:
Code:
IP=$(curl -s queryip.net/ip/)
URL=$(curl -s queryip.net/url/)

# 6  
Quote:
Originally Posted by KenJackson
I like my method of finding my local IP address better:
Hi,

I actually have to find the IP address of another server on the same LAN given its MAC address.
Thanks for sharing your ideas and code!

M.
# 7  
Just for the fun of it Smilie
Code:
echo "Your ip is:" $(/sbin/arp -a | grep 00:00:44:00:01:44 | awk -F'[(|)]' '{print $2}')


Last edited by Franklin52; 06-08-2011 at 03:56 AM.. Reason: Please use code tags, thank you

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