Variable inside bash's while loop never changed

Question

Why does the following code always outputs "0"?

#!/bin/bash

RETVAL=0
echo -e '1\n2' | while read number; do
    RETVAL=1
done

echo $RETVAL

Answer 1

The while loop is part of a pipeline, and therefore runs in a subshell. Variables set in the subshell (RETVAL=1) don't affect the parent shell (echo $RETVAL).

Answer 2

It has to do with how the echo is not passing an EOF / Ctrl D to the while read.

If you pull the echo out and enter a Ctrl D to the while loop it will work as expected.

Not sure how to send a Ctrl D via an echo.