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If you don't mind using Bash,
then it will be more elegant to replace the while loop with a counting for loop:

for ((i = 0; ; i++)); do
    # ...
done


I'm guessing that you're using Bash anyway from the let "i++" syntax,
which will not work with simpler shells like Dash.

Note that the various flags of echo are not portable.
For a more portable solution, replace it with printf.

Lastly, the indentation is inconsistent: some blocks are indented with 4 spaces, others with 2. It would be better to indent consistently (I like 4 spaces).