Bash: Split two strings directly into associative array - bash

Question

I have two strings of same number of substrings divided by a delimiter.
I need to create key-value pairs from substrings.
Short example:
Input:
firstString='00011010:00011101:00100001'
secondString='H:K:O'
delimiter=':'
Desired result:
${translateMap['00011010']} -> 'H'
${translateMap['00011101']} -> 'K'
${translateMap['00100001']} -> 'O'
So, I wrote:
IFS="$delimiter" read -ra fromArray <<< "$firstString"
IFS="$delimiter" read -ra toArray <<< "$secondString"
declare -A translateMap
curIndex=0
for from in "${fromArray[#]}"; do
translateMap["$from"]="${toArray[curIndex]}"
((curIndex++))
done
Is there any way to create the associative array directly from 2 strings without the unneeded arrays and loop? Something like:
IFS="$delimiter" read -rA translateMap["$(read -ra <<< "$firstString")"] <<< "$secondString"
Is it possible?

Answer 1

A (somewhat convoluted) variation on #accdias's answer of assigning the values via the declare -A command, but will need a bit of explanation for each step ...
First we need to break the 2 variables into separate lines for each item:
$ echo "${firstString}" | tr "${delimiter}" '\n'
00011010
00011101
00100001
$ echo "${secondString}" | tr "${delimiter}" '\n'
H
K
O
What's nice about this is that we can now process these 2 sets of key/value pairs as separate files.
NOTE: For the rest off this discussion I'm going to replace "${delimiter}" with ':' to make this a tad bit (but not much) less convoluted.
Next we make use of the paste command to merge our 2 'files' into a single file; we'll also designate ']' as the delimiter between key/value mappings:
$ paste -d ']' <(echo "${firstString}" | tr ':' '\n') <(echo "${secondString}" | tr ':' '\n')
00011010]H
00011101]K
00100001]O
We'll now run these results through a couple sed patterns to build our array assignments:
$ paste -d ']' <(echo "${firstString}" | tr ':' '\n') <(echo "${secondString}" | tr ':' '\n') | sed 's/^/[/g;s/]/]=/g'
[00011010]=H
[00011101]=K
[00100001]=O
What we'd like to do now is use this output in the typeset -A command but unfortunately we need to build the entire command and then eval it:
$ evalstring="typeset -A kv=( "$(paste -d ']' <(echo "${firstString}" | tr ':' '\n') <(echo "${secondString}" | tr ':' '\n') | sed 's/^/[/g;s/]/]=/g')" )"
$ echo "$evalstring"
typeset -A kv=( [00011010]=H
[00011101]=K
[00100001]=O )
If we want to remove the carriage returns and put on a single line we append another tr at the output from the sed command:
$ evalstring="typeset -A kv=( "$(paste -d ']' <(echo "${firstString}" | tr ':' '\n') <(echo "${secondString}" | tr ':' '\n') | sed 's/^/[/g;s/]/]=/g' | tr '\n' ' ')" )"
$ cat "${evalstring}"
typeset -A kv=( [00011010]=H [00011101]=K [00100001]=O )
At this point we can eval our auto-generated typeset -A command:
$ eval "${evalstring}"
And now loop through our array displaying the key/value pairs:
$ for i in ${!kv[#]}; do echo "kv[${i}] = ${kv[${i}]}"; done
kv[00011010] = H
kv[00100001] = O
kv[00011101] = K
Hey, I did say this would be a bit convoluted! :-)

Answer 2

It is probably not what you expect, but this works:
key_string="A:B:C:D"
val_string="1:2:3:4"
declare -A map
while [ -n "$key_string" ] && [ -n "$val_string" ]; do
IFS=: read -r key key_string <<<"$key_string"
IFS=: read -r val val_string <<<"$val_string"
map[$key]="$val"
done
for key in "${!map[#]}"; do echo "$key => ${map[$key]}"; done
It uses recursion in the read function to reassign the string value.
The downside of this method is that it destroys the original strings. The while-loop checks constantly if both strings have a non-zero length.
Next to the above in pure bash, you could any command to generate the associative array. See How do I populate a bash associative array with command output?
This generally looks like:
declare -A map="( $( magic_command ) )"
where the magic_command generates an output like
[key1]=val1
[key2]=val2
[key3]=val3
In this case we use the command:
paste -d "" <(echo "[${key_string//:/]=$'\n'[}]=") \
<(echo "${val_string//:/$'\n'}")
where we use bash substitution to replace the delimiter with a newline. However, any other magic_command might do. For completion:
key_string="A:B:C:D"
val_string="1:2:3:4"
declare -A map="( $(paste -d "" <(echo "[${key_string//:/]=$'\n'[}]=") \
<(echo "${val_string//:/$'\n'}")) )"
for key in "${!map[#]}"; do echo "$key => ${map[$key]}"; done
Both examples generate the following output
D => 4
C => 3
B => 2
A => 1

Answer 3

Not exactly the answer for what you asked but at least it is shorter:
key='00011010:00011101:00100001'
value='H:K:O'
ifs=':'
IFS="$ifs" read -ra keys <<< "$key"
IFS="$ifs" read -ra values <<< "$value"
declare -A kv
for ((i=0; i<${#keys[*]}; i++)); do
kv[${keys[i]}]=${values[i]}
done
As a side note, you can initialize an associative array in one step with:
declare -A kv=([key1]=value1 [key2]=value2 [keyn]=valuen)
But I don't know how to use that in your case.

Answer 4

If values in your strings won't use spaces i would suggest this approach
firstString='00011010:00011101:00100001'
secondString='H:K:O'
delimiter=':'
declare -A translateMap
firstArray=( ${firstString//$delimiter/' '} )
secondArray=( ${secondString//$delimiter/' '} )
for i in ${!firstArray[#]}; {
translateMap[firstArray[$i]}]=${secondArray[$i]}
}