As Michael Vehrs said, bash's associative arrays do not preserve insertion ordering. This is a "feature" of associative arrays in general. The "magic" for this in bash happens in hashlib.c.

Bash does have indexed arrays, which you could use as an indicator for the insertion order:

declare -A REPLACE_MAP
declare -a REPLACE_MAP_INDEX
REPLACE_MAP['b']='2'
REPLACE_MAP_INDEX+=('b')
REPLACE_MAP['a']='1'
REPLACE_MAP_INDEX+=('a')
for key in "${REPLACE_MAP_INDEX[@]}"; do
    printf "%s - %s\n" "$key" "${REPLACE_MAP["$key"]}"
    value=${REPLACE_MAP["$key"]}
done

Another option, depending on your data, is a single indexed array whose values are the original key and value combined in some way (here, using a space):

unset arr
declare -a arr
arr+=("b 2")
arr+=("a 1")
for ckey in "${arr[@]}"; do
  key=${ckey% *}
  value=${ckey#* }
  printf "%s - %s\n" "$key" "$value"
done

... but if space is a valid part of a key or a value, then pick something else that's unused, such as a pipe symbol for example:

unset arr
declare -a arr
arr+=("b|2")
arr+=("a|1")
for ckey in "${arr[@]}"; do
  key=${ckey%|*}
  value=${ckey#*|}
  printf "%s - %s\n" "$key" "$value"
done

As Michael Vehrs said, bash's associative arrays do not preserve insertion ordering. This is a "feature" of associative arrays in general. The "magic" for this in bash happens in hashlib.c.

Bash does have indexed arrays, which you could use as an indicator for the insertion order:

declare -A REPLACE_MAP
declare -a REPLACE_MAP_INDEX
REPLACE_MAP['b']='2'
REPLACE_MAP_INDEX+=('b')
REPLACE_MAP['a']='1'
REPLACE_MAP_INDEX+=('a')
for key in "${REPLACE_MAP_INDEX[@]}"; do
    printf "%s - %s\n" "$key" "${REPLACE_MAP["$key"]}"
    value=${REPLACE_MAP["$key"]}
done

Another option, depending on your data, is a single indexed array whose values are the original key and value combined in some way (here, using a space):

unset arr
declare -a arr
arr+=("b 2")
arr+=("a 1")
for ckey in "${arr[@]}"; do
  key=${ckey% *}
  value=${ckey#* }
  printf "%s - %s\n" "$key" "$value"
done

... but if space is a valid part of a key or a value, then pick something else that's unused, such as a pipe symbol for example:

unset arr
declare -a arr
arr+=("b|2")
arr+=("a|1")
for ckey in "${arr[@]}"; do
  key=${ckey%|*}
  value=${ckey#*|}
  printf "%s - %s\n" "$key" "$value"
done

As Michael Vehrs said, bash's associative arrays do not preserve insertion ordering. This is a general "feature" of associative arrays in general. The "magic" for this in bash happens in hashlib.c.

Bash does have indexed arrays, which you could use as an indicator for the insertion order:

declare -A REPLACE_MAP
declare -a REPLACE_MAP_INDEX
REPLACE_MAP['b']='2'
REPLACE_MAP_INDEX+=('b')
REPLACE_MAP['a']='1'
REPLACE_MAP_INDEX+=('a')
for key in "${REPLACE_MAP_INDEX[@]}"; do
    printf "%s - %s\n" "$key" "${REPLACE_MAP["$key"]}"
    value=${REPLACE_MAP["$key"]}
done

Another option, depending on your data, is a single indexed array whose values are the original key and value combined in some way (here, using a space):

unset arr
declare -a arr
arr+=("b 2")
arr+=("a 1")
for ckey in "${arr[@]}"; do
  key=${ckey% *}
  value=${ckey#* }
  printf "%s - %s\n" "$key" "$value"
done

... but if space is a valid part of a key or a value, then pick something else that's unused, such as a pipe symbol for example:

unset arr
declare -a arr
arr+=("b|2")
arr+=("a|1")
for ckey in "${arr[@]}"; do
  key=${ckey%|*}
  value=${ckey#*|}
  printf "%s - %s\n" "$key" "$value"
done

As Michael Vehrs said, bash's associative arrays do not preserve insertion ordering. This is a "feature" of associative arrays in general. The "magic" for this in bash happens in hashlib.c.

Bash does have indexed arrays, which you could use as an indicator for the insertion order:

declare -A REPLACE_MAP
declare -a REPLACE_MAP_INDEX
REPLACE_MAP['b']='2'
REPLACE_MAP_INDEX+=('b')
REPLACE_MAP['a']='1'
REPLACE_MAP_INDEX+=('a')
for key in "${REPLACE_MAP_INDEX[@]}"; do
    printf "%s - %s\n" "$key" "${REPLACE_MAP["$key"]}"
    value=${REPLACE_MAP["$key"]}
done

Another option, depending on your data, is a single indexed array whose values are the original key and value combined in some way (here, using a space):

unset arr
declare -a arr
arr+=("b 2")
arr+=("a 1")
for ckey in "${arr[@]}"; do
  key=${ckey% *}
  value=${ckey#* }
  printf "%s - %s\n" "$key" "$value"
done

... but if space is a valid part of a key or a value, then pick something else that's unused, such as a pipe symbol for example:

unset arr
declare -a arr
arr+=("b|2")
arr+=("a|1")
for ckey in "${arr[@]}"; do
  key=${ckey%|*}
  value=${ckey#*|}
  printf "%s - %s\n" "$key" "$value"
done