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Calling a Variable based on a Variable

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# 1  
Old 06-04-2013
Calling a Variable based on a Variable
Hi all,

I have a source config file with variables like so:
Code:
eth1_ip=192.168.1.99
eth2_ip=192.168.1.123
eth3_ip=172.16.1.1

I am trying to run a script which loops based on the number of eth interfaces on a machine and therefore modifies the variable it calls in the environment based on the interface in each loop:

Code:
source config.conf
for int in `ip link |grep eth[0-7] |cut -d " " -f 2|cut -d":" -f1`; do

echo $int_ip

done

Any ideas??

thanks,Ll
# 2  
Old 06-04-2013
Code:
links=$(ip link |grep eth[0-7] |cut -d " " -f 2|cut -d":" -f1` | tr -s '\n' ' ')
for i in $links
do
  echo $i
done

Is that what you are asking -- not clear to me, so I guessed. The cut and chop probably should be replaced with an awk call.
Code:
links=$(ip link |grep eth[0-7] | awk -F '[ :]' '{printf("%s ", $3)}')

This User Gave Thanks to jim mcnamara For This Post:
landossa
# 3  
Old 06-05-2013
That is what the current code does.
But I need it to source the variables from config.conf being;
Code:
eth1_ip=192.168.1.99
eth2_ip=192.168.1.123
eth3_ip=172.16.1.1

And re-write the variable from the config file so that it will echo;
Code:
192.168.1.99
192.168.1.123 
172.16.1.1

for variables;
Code:
eth1_ip
eth2_ip
eth3_ip

so the statement needs to look something like;
Code:
echo $($int"_ip")

But the above statement is only my guess.

---------- Post updated 06-06-13 at 12:17 AM ---------- Previous update was 05-06-13 at 12:58 PM ----------

Ok I have cracked it:
Code:
# config.conf
eth1_ip=192.168.1.1

Code:
source config.conf
for int in `ip link |grep eth[0-7] |cut -d " " -f 2|cut -d":" -f1`; do

ethip=$"$int"_ip

echo ${!ethip}        # This gives the output I was looking for.

done

Last edited by landossa; 06-05-2013 at 07:41 PM..
This User Gave Thanks to landossa For This Post:
vbe
# 4  
Old 06-05-2013
Thanks for informing us !
# 5  
Old 06-06-2013
Note that ${! ... } is a bashism and does not work in other shells.

A more portable method is to use eval, i.e.
Code:
eth1_ip=192.168.1.1
int=eth1

ethip=$"$int"_ip
eval echo \$${ethip}

# 6  
Old 06-06-2013
Or better yet, just use an array. Dynamic variable names are seldom a good idea. You can get the length of an array, for instance, but cannot easily tell how many eth? variables you have.
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