variable variables in BASH

Question

I would like to ask some help regarding variable variables in bash. I've read a few articles about it, but in my case I don't know how to do it. Let see my problem:

The array contains other arrays' names and I want to print the values of these arrays. In inner for I need variable variables.

#!/bin/bash
declare -a array=(dir1 dir2 dir3)
declare -a dir1=(1 2 3)
declare -a dir2=(a b c)
declare -a dir3=(9 8 7)

for elem1 in "${array[@]}"
do
  for elem2 in "${variableVariable[@]}"
  do
    echo "$elem1 : $elem2"
  done
done

The output should be something like this

dir1 : 1
dir1 : 2
dir1 : 3
dir2 : a
dir2 : b
dir2 : c
dir3 : 9
dir3 : 8
dir3 : 7

Don't use variable variables in this case. Use associative arrays. — Alex
– Alex, Commented May 2, 2013 at 5:52
possible duplicate of Lookup shell variables by name, indirectly — tripleee
– tripleee, Commented May 2, 2013 at 6:01
@tripleee It's similar to that question, but there's some extra work you have to do to deal with [@] when indirecting. It took me a while to figure it out. — Barmar
– Barmar, Commented May 2, 2013 at 7:34
Mine problem is the how to deal with [@] part of the script. Can you help me? — AndrasCsanyi
– AndrasCsanyi, Commented May 3, 2013 at 18:02

Barmar · Accepted Answer · 2013-05-02 05:58:48Z

7

This can be done using bash's indirect variable feature.

for elem1 in "${array[@]}"
do
  elems=$elem1'[@]'
  for elem2 in "${!elems}"
  do
    echo "$elem1 : $elem2"
  done
done

Note that this is a bash extension, it's not portable to other shells.

answered May 2, 2013 at 5:58

Barmar

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1 Comment

AndrasCsanyi Over a year ago

I'll take a look at it. I would like to run my script in git shell on windows.

AndrasCsanyi · Accepted Answer · 2013-05-06 07:37:14Z

0

Finally, I found the solution. I had to use eval because I was not able to deal with the other syntax, I mean the composition of the ${!variable} and the ${variable[@]}.

#!/bin/bash
declare -a array=(dir1 dir2 dir3)
declare -a dir1=(1 2 3)
declare -a dir2=(a b c)
declare -a dir3=(9 8 7)

for elem1 in "${array[@]}"
do
  for elem2 in `eval echo \$\{$elem1\[@\]\}"`
  do
    echo "$elem1 : $elem2"
  done
done

edited May 6, 2013 at 7:37

answered May 5, 2013 at 12:42

AndrasCsanyi

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