[jpavel2]

I'm not seeing this local scope leak with bash 5.2.15. The below script works as I'd expect:

  #!/bin/bash
  
  declare -A map1=([x]=2)
  echo "1. Global scope map1[x]: ${map1[x]}"
  
  func1() {
      echo " * Enter func1"
      local -A map1
      map1[x]=3
      echo "   Local scope map1[x]: ${map1[x]}"
  }
  
  func1
  
  echo "2. Global scope map1[x]: ${map1[x]}"

outputting

  1. Global scope map1[x]: 2
   * Enter func1
     Local scope map1[x]: 3
  2. Global scope map1[x]: 2

[syntacticbs]

The local scope leak seems to only happen when you drop down the call stack. See below how I can call func2 from the top level and it's fine, but if I call it from within func1, it will leak.

  #!/bin/bash
  
  declare -A map1=([x]=2)
  echo "1. Global scope map1[x]: ${map1[x]}"
  func1() {
      echo " * Enter func1"
      local -A map1
      map1[x]=3
      echo "   Local scope map1[x]: ${map1[x]}"
      func2
  }
  func2() {
      echo "  * Enter func2"
      echo "      Local scope map1[x]: ${map1[x]}"
  }
  func1
  func2
  echo "2. Global scope map1[x]: ${map1[x]}"

outputing: 1. Global scope map1[x]: 2 * Enter func1 Local scope map1[x]: 3 * Enter func2 Local scope map1[x]: 3 * Enter func2 Local scope map1[x]: 2 2. Global scope map1[x]: 2

UPDATE: I did a bit of exploration and it turns out ANY variable declared `local` is in the scope of a function lower down in the call stack. But if you declare a variable as `local` in a called function that shadows the name of a variable in a callee function, it will shadow the callee's name and reset the variable back to the vallee's value when the function returns. I have been writing bash for years and did not realise this is the case. It is even described in the man page: When local is used within a function, it causes the variable name to have a visible scope restricted to that function and its children.

Thank you. You have taught me two things today. One is a bash feature I did not know existed. The second is a new reason to avoid writing complex bash.

[layer8]

This is know as dynamic scope, as opposed to lexical scope: https://en.wikipedia.org/wiki/Scope_(computer_science)#Lexic...