# Verify that `read -t 0 v` succeeds immediately if input is available
# and fails immediately if not

set -e

T=$(mktemp -d ${TMPDIR:-/tmp}/sh-test.XXXXXX)
trap 'rm -rf "$T"' 0
cd $T
mkfifo fifo1
# Open fifo1 for writing
{ echo new_value; sleep 10; } >fifo1 &
# Wait for the child to open fifo1 for writing
exec 3<fifo1

v=original_value
r=0
ts=$(date +%s%3N)
read -t 0 v <&3 || r=$?
te=$(date +%s%3N)
[ "$r" -eq 0 ]
[ $((te-ts)) -lt 250 ]
[ "$v" = "new_value" ]

v=original_value
r=0
ts=$(date +%s%3N)
read -t 0 v <&3 || r=$?
te=$(date +%s%3N)
kill -TERM "$!" || :
[ "$r" -gt 128 ] && [ "$(kill -l "$r")" = ALRM ]
[ $((te-ts)) -lt 250 ]
[ -z "$v" ]