OFS
(Output Field Separator) is ignored when using { print }
instead of { print $1,$2,$3... }
.
awk '{$1=$1};1' input.txt
# The following shows:
# apple
# pineapple
echo "apple\norange\npineapple" | awk '/apple/ { print $0 }'
awk -F, '{print $NF}' input.txt