I searched the site, but can find an answer to my problem.

I'm building an array from stdin and need to filter for unique lines. To do this, I'm using awk '!x[$0]++' which I've read is shorthand for:

awk 'BEGIN { while (getline s) { if (!seen[s]) print s; seen[s]=1 } }'.

The filter works as desired but the issue is that the resulting array from the while read loop is empty.

For example (using $list as a surrogate for stdin):

list=$'red apple\nyellow banana\npurple grape\norange orange\nyellow banana'
while read -r line; do
    array[count++]=$line
done <<< "$list"
echo "array length = ${#array[@]}"
counter=0
while [  $counter -lt ${#array[@]} ]; do
    echo ${array[counter++]}
done

produces:

array length = 5
red apple
yellow banana
purple grape
orange orange
yellow banana

But filtering $list with awk:

list=$'red apple\nyellow banana\npurple grape\norange orange\nyellow banana'
awk '!x[$0]++' <<< "$list" | while read -r line; do
    array[count++]=$line
done
echo "array length = ${#array[@]}"
counter=0
while [  $counter -lt ${#array[@]} ]; do
     echo ${array[counter++]}
done

produces:

array length = 0

But the output of awk '!x[$0]++' <<< "$list" appears fine:

red apple
yellow banana
purple grape
orange orange

I've tried examining each line in the while read loop:

list=$'red apple\nyellow banana\npurple grape\norange orange\nyellow banana'
i=0
awk '!x[$0]++' <<< "$list" | while read -r line; do
    echo "line[$i] = $line"
    let i=i+1
done

and it appears fine:

line[0] = red apple
line[1] = yellow banana
line[2] = purple grape
line[3] = orange orange

What am I missing here?

In case it's important, I'm using bash 3.2.57:

GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin15) Copyright (C) 2007 Free Software Foundation, Inc.