concatenate strings in bash

sadosan83 · 01-11-2012, 05:57 AM

hi all

node1_pc_ip=10.20.5.10
node1_modem_ip=192.168.2.10
node2_pc_ip=10.20.5.20
node2_modem_ip=192.168.2.20

for i in $(seq "$node")
do

echo $node$i_pc_ip

done

echo $node$i_pc_ip now working , output is;
1_pc_ip
2_pc_ip
3_pc_ip
.
I would like to output is ;

10.20.5.10
10.20.5.11
10.20.5.12

help me pls

millgates · 01-11-2012, 07:05 AM

Hello,
1) what is seq "$node" supposed to do?
2) I'm not sure I understand what you want to do, but have you tried

Code:

eval echo \$node${i}_pc_ip

EDIT: 3) or, even better, use arrays

BenCollver · 01-11-2012, 07:32 AM

Or

varname="node${i}_pc_ip"
echo ${!varname}

sadosan83 · 01-11-2012, 08:29 AM

Quote:

Originally Posted by millgates

Hello,
1) what is seq "$node" supposed to do?
2) I'm not sure I understand what you want to do, but have you tried

Code:

eval echo \$node${i}_pc_ip

EDIT: 3) or, even better, use arrays

thanks ... fixed

David the H. · 01-11-2012, 11:08 AM

Aargh. No, no, no! Please do not use indirect variables for things like this. And for goodness sake, stay away from eval.

As suggested, this is exactly the kind of thing you should be using arrays for.

Code:

node_pc_ip=( 10.20.5.10 10.20.5.20 )
node_modem_ip=( 192.168.2.10 192.168.2.20 )

for i in {1..2}; do

	echo "${node_pc_ip[i]}"
	echo "${node_modem_ip[i]}"

done

Please stop and take the time to read the BashGuide here, to help you understand basic scripting concepts such as arrays.

http://mywiki.wooledge.org/BashGuide

Then at least scan through the pitfalls and faq pages for more pointers and things to be aware of, such as the importance of proper quoting and using brace expansion (or a c-style loop) instead of seq:

http://mywiki.wooledge.org/BashPitfalls
http://mywiki.wooledge.org/BashFAQ

Finally, please use [code][/code] tags around your code and data, to preserve formatting and to improve readability.

Nominal Animal · 01-12-2012, 03:02 PM

I agree with David the H., except that since Bash uses zero-based indexing, I do believe the example snippet should read

Code:

node_pc_ip=( 10.20.5.10 10.20.5.20 )
node_modem_ip=( 192.168.2.10 192.168.2.20 )

for i in {0..1}; do

	echo "${node_pc_ip[i]}"
	echo "${node_modem_ip[i]}"

done

David the H. · 01-12-2012, 09:45 PM

D'oh!

Thanks for catching my mistake, NA.

sadosan83 · 01-13-2012, 01:48 AM

Quote:

Originally Posted by David the H.

D'oh!

Thanks for catching my mistake, NA.

thanks all member
resolf pls