Double Interpolation of Array in Bash

Question

I'm trying to make a script so that I can easily add host types to it without changing the code itself. Each type of host has a specific group of id's and templates associated with it. Here is the cod that I have derived:

CLASS="memcache"
memcache_template=( 42 45 )
CLASS_template=${CLASS}_template
template=$( eval echo $`echo $CLASS_template` )

for i in  ${template[@]}; do
  echo $i
done

The output that I get is just "42". I need it to output both 42 and 45.

Michael Hoffman · Accepted Answer · 2011-10-26 20:39:49Z

3

Here's a way to do it:

CLASS="memcache"
memcache_template=(42 45)

CLASS_template=${CLASS}_template[@]

for i in ${!CLASS_template}; do
  echo $i
done

See the discussion of variable indirection in info "(bash)Shell Parameter Expansion". Note that you cannot use ${!CLASS_template[@]} because that has a special meaning. The array subscripting must be done before indirection.

edited Oct 26, 2011 at 20:39

answered Oct 26, 2011 at 0:18

Michael Hoffman

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2 Comments

Gordon Davisson Over a year ago

Neat! Also, you could put memcache_template's contents into a new array (more similar to the code in the question) with template=("${!CLASS_template}")

Jericon Over a year ago

Actually, I found that I can skip a whole step. I simply defined template=( "${CLASS}_template[@]" ).

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