How to pass an associative array as argument to a function in Bash?

Question

How do you pass an associative array as an argument to a function? Is this possible in Bash?

The code below is not working as expected:

function iterateArray {     local ADATA="${@}"            # associative array  for key in "${!ADATA[@]}" do     echo "key - ${key}"     echo "value: ${ADATA[$key]}"  done  } 

Passing associative arrays to a function like normal arrays does not work:

iterateArray "$A_DATA" 

or

iterateArray "$A_DATA[@]" 

Answer 1

I had exactly the same problem last week and thought about it for quite a while.

It seems, that associative arrays can't be serialized or copied. There's a good Bash FAQ entry to associative arrays which explains them in detail. The last section gave me the following idea which works for me:

function print_array {     # eval string into a new associative array     eval "declare -A func_assoc_array="${1#*=}     # proof that array was successfully created     declare -p func_assoc_array }  # declare an associative array declare -A assoc_array=(["key1"]="value1" ["key2"]="value2") # show associative array definition declare -p assoc_array  # pass associative array in string form to function print_array "$(declare -p assoc_array)"  

Answer 2

If you're using Bash 4.3 or newer, the cleanest way is to pass the associative array by name and then access it inside your function using a name reference with local -n. For example:

function foo {     local -n data_ref=$1     echo ${data_ref[a]} ${data_ref[b]} }  declare -A data data[a]="Fred Flintstone" data[b]="Barney Rubble" foo data 

You don't have to use the _ref suffix; that's just what I picked here. You can call the reference anything you want so long as it's different from the original variable name (otherwise youll get a "circular name reference" error).