How to nest a variable inside a variable?

Question

I have a scenario in which I need to execute the below statement.

air sandbox run $AI_PLAN/Sam_22.plan

For the above command AI should be fetched from a command.

> echo $PREFIX
AI

I tried the below ways

air sandbox run $`echo $PREFIX`_PLAN/Sam_22.plan

returned error : File not found

dollar_prefix=$`echo $PREFIX`
air sandbox run ${dollar_prefix}_PLAN/Sam_22.plan

returned error : File not found

Please let me know where am I going wrong in the above coding.

glenn jackman · Accepted Answer · 2011-08-09 23:40:19Z

1

You're going to need to eval something:

PREFIX=AI
AI_PLAN=some_directory
eval directory=\$${PREFIX}_PLAN
air sandbox run $directory/Sam_22.plan

answered Aug 9, 2011 at 23:40

glenn jackman

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Comments

Foo Bah · Accepted Answer · 2011-08-09 22:56:48Z

0

try using command substitution:

$(command ...)_PLAN

Lets suppose the program make_prefix is in your path. Then:

> make_prefix
AI
> echo $(make_prefix)
AI
> echo $(make_prefix)_PLAN
AI_PLAN

answered Aug 9, 2011 at 22:56

Foo Bah

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2 Comments

user840963 Over a year ago

Hi Foo Bah, I did not understand clearly can you please eloborate.

user840963 Over a year ago

Hi Foo, this did not work out it is giving error message.Thank you.

Chris Dodd · Accepted Answer · 2011-08-09 23:07:51Z

0

It unclear what you actually want to have happen, but I can guess that you probably want something like

air sandbox ${${PREFIX}_PLAN}/Sam_22.plan

This will take the value of the variable PREFIX (AI in your case?) and append a _PLAN, and use THAT as the name of a variable to fetch

answered Aug 9, 2011 at 23:07

Chris Dodd

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1 Comment

user840963 Over a year ago

Hi Chris, Thanks for answering I am getting below error > echo ${PREFIX} AI > echo ${PREFIX}_PLAN AI_PLAN > echo ${${PREFIX}_PLAN} -ksh: syntax error: `!' unexpected

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