Multidimensional associative arrays in Bash

Question

I'm trying to create a multidimensional associative array but need some help. I have reviewed the page suggested in this SO answer but it confused me even more. So far here is what I have:

The script:

#!/bin/bash declare -A PERSONS declare -A PERSON PERSON["FNAME"]='John' PERSON["LNAME"]='Andrew' PERSONS["1"]=${PERSON[@]} PERSON["FNAME"]='Elen' PERSON["LNAME"]='Murray' PERSONS["2"]=${PERSON[@]} for KEY in "${!PERSONS[@]}"; do  TMP="${PERSONS["$KEY"]}"  echo "$KEY - $TMP"  echo "${TMP["FNAME"]}"  echo "${TMP["LNAME"]}" done 

The output:

1 - John Andrew John Andrew John Andrew 2 - Elen Murray Elen Murray Elen Murray 

As you can see trying to access a specific index of the $TMP array in the for loop returns the whole array.

[Q] What do I need to do in order to separately access the "FNAME" and "LNAME" indexes of the $TMP array inside the for loop?

Thanks.

Answer 1

You can't do what you're trying to do: bash arrays are one-dimensional

$ declare -A PERSONS $ declare -A PERSON $ PERSON["FNAME"]='John' $ PERSON["LNAME"]='Andrew' $ declare -p PERSON declare -A PERSON='([FNAME]="John" [LNAME]="Andrew" )' $ PERSONS[1]=([FNAME]="John" [LNAME]="Andrew" ) bash: PERSONS[1]: cannot assign list to array member 

You can fake multidimensionality by composing a suitable array index string:

declare -A PERSONS declare -A PERSON  PERSON["FNAME"]='John' PERSON["LNAME"]='Andrew' i=1 for key in "${!PERSON[@]}"; do   PERSONS[$i,$key]=${PERSON[$key]} done  PERSON["FNAME"]='Elen' PERSON["LNAME"]='Murray' ((i++)) for key in "${!PERSON[@]}"; do   PERSONS[$i,$key]=${PERSON[$key]} done  declare -p PERSONS # ==> declare -A PERSONS='([1,LNAME]="Andrew" [2,FNAME]="Elen" [1,FNAME]="John" [2,LNAME]="Murray" )'