reference variable which is assigned value from another variable

Question

I have following shell script -

AWSZONE="central"
ENVIRONMENT="staging"
REMOTE_HOSTS_central_staging="172.31.7.59,172.31.3.151
NAME="REMOTE_HOSTS_${AWSZONE}_${ENVIRONMENT}"
echo "Using following agents: ${NAME}"

When executing I get following output -

Using following agents: REMOTE_HOSTS_central_staging

Though I would like to get output -

Using following agents: 172.31.7.59,172.31.3.151

What is wrong with my syntax?

Possible duplicate of [how to use a variable's value as other variable's name in bash](http://stackoverflow.com/questions/9714902/how-to-use-a-variables-value-as-other-variables-name-in-bash) — Julien Lopez, Mar 30 '16 at 09:37

score 2 · Accepted Answer · answered Mar 30 '16 at 09:29

2

Change the echo to

echo "Using following agents: ${!NAME}"

And it should be OK.

answered Mar 30 '16 at 09:29

LarsErik

138
1
7

works well, is there a special name for using negation symbol before variable name? – Tarun Mar 30 '16 at 09:42
Its called indirect expansion. It is mentioned in the bash man pages under Parameter Expansion :-) – LarsErik Mar 30 '16 at 09:45

Ren · Answer 2 · 2016-03-30T09:43:29.907

1

Try this:

AWSZONE="central"
ENVIRONMENT="staging"
REMOTE_HOSTS_central_staging="172.31.7.59,172.31.3.151"
NAME="REMOTE_HOSTS_${AWSZONE}_${ENVIRONMENT}"
eval "echo Using following agents: \$${NAME}"

Output:

Using following agents: 172.31.7.59,172.31.3.151

If you use bash, you can also use @LarsErik's answer.It is known as Indirect Expansion

edited Mar 30 '16 at 09:43

answered Mar 30 '16 at 09:35

Ren

2,852
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reference variable which is assigned value from another variable

2 Answers2