UNIX for Dummies Questions & Answers

I'm new to BASH and i'm trying to create a script which is simply put a large find and replace file. This is what I have so far


N=0
while read LINE ; do

N=$((N+1))

sed 's/'$2'/'$3'/g' $LINE > .temp
echo "Changes to file $N = $LINE"
echo 'The following changes will be made will be made to $LINE :'
diff .temp $LINE
echo 'Are you sure you want to make these changes? y/
readline a

if [[ $a == "N" || $a == "n" || $a == "No" || $a == "no" ]]; then
echo "No changes have been made to $LINE"
rm .tempfr

elif [[ $a == "Y" || $a == "y" || $a == "Yes" || $a == "yes" ]]; then

mv .tempfr $LINE
echo "The given changes have been made successfully"

else
echo $a "is not a recognized input. Please use y/n"

fi
rm .temp
done < $1



For this code the $1 is a file which is simply a list of files which need to be searched with this find and remove script. $2 is the word that i'm looking to find and $3 is the word i'm looking to replace it with. The problem that I seem to be having is that every time that I run this script it seems to skip the

read a

line, and assumes that the user put in no input. I'm worried that this has something to do with using two read commands but I don't exactly know what the problem would be. Does anyone know why it isn't allowing me to ask for user input from inside this while loop?

Code:

echo 'Are you sure you want to make these changes? y/n '
read  -sn1 a < $(tty)

As loops are executed in a subshell, they can't read from the same stdin as the script is executed.

I'm afraid I don't fully understand. I see the logic in attaching the -sn1 to the read file. That makes it accept y, Y, yes, Yes, n, N, no, and No without having to go through the whole if or statement that I wrote. But I don't know what the -a < $(tty) does. and I don't see how it would help me deal with the stdin issue.
Do you know of a way I could write my code to get around that?

sorry, 'a' is not part of read options: it's not '-a', it's ' a' your variable's name.

I've edited my post to correct my typo.

Specific tty is not needed actually, /dev/tty should do

well, how?
As I can launch a script from /dev/pts/'any munber', or a real /dev/tty'any number', how else could you determine what "tty" should give the input?