Using a pipe inside a for loop. How do I preserve the value of the variable inside the for loop - bash

Question

I've been stuck for quite some time with the following code. It works but the variable loses the value that was set during the iterations.
I have the following code
mistakes=0
entered_chars=()
word_length=0
answer=""
answer_guess=""
checkIfLetterInsideWord(){
exists=0
letter=$2
word_array=`echo $1 | grep -o . `;
for (( i=1; i <= $word_length; i++))
do
if [[ "${1:$i-1:1}" = ${letter} ]]; then
exists=1
answer_guess=$(echo $answer_guess | sed "s/-/${letter}/{i}" )
fi
done
echo $exists
}
askUserInput(){
answer=$answer
echo $answer
echo "Please type a letter"
read user_input
if [ ! -z $user_input ]; then
user_input=$(echo $user_input | tr '[:upper:]' '[:lower:]')
if [ $(checkIfAlreadyEntered "$user_input") -eq 0 ]; then
if [ $(checkIfLetterInsideWord $answer $user_input) -eq 0 ]; then
mistakes=$((mistakes + 1)); fi
echo "Current mistake count; $mistakes "
entered_chars+=($user_input)
else
echo "Char has already been entered"
fi
else
echo "You haven't entered any input!"
fi
}
guessTheWord() {
answer=$OPTARG
word_length=$(printf $answer | wc -m)
temp=$(echo $answer | sed 's/\(.\)/\1 /g')
array=($temp)
echo "The chosen word is $word_length long"
gameOngoing=true
for(( i=1; i<=$word_length; i++)) do
answer_guess="$answer_guess-"
done
while $gameOngoing
do
echo $answer_guess
askUserInput $answer
done
}
I want to preserve the value of the variable answer_guess. I understand that it loses the value because of the usage of a pipeline inside the loop but I don't know to approach this problem.

Answer 1

The problem has nothing do to with the pipe. Rather, it is that you call checkIfLetterInsideWord inside a command-substitution ($(...)). Command substitution executes in a subshell so environment changes in the function will not persist.
It would be better to rewrite checkIfLetterInsideWord so that it returns an exit status. Something like:
if [[ $exists ]]; then
return 0 # Success
else
return 1 # Failure
end
Then you could simply call it without worrying about a subshell:
if checkIfLetterInsideWord "$answer" "$user_input"; then
# letter is in word
else
# letter is not in word
fi
There are other issues with the code. I've limited this answer to the question about preserving the value of variables.

Answer 2

answer_guess=$(echo $answer_guess | sed "s/-/${letter}/{i}" )
replace the - with .
so your code becomes
answer_guess=$(echo $answer_guess | sed "s/./${letter}/{i}" )