unset LC_ALL
LC_CTYPE=en_US.ISO8859-1
export LC_CTYPE

# Note: the first and last characters are not whitespace.
# Exclude backslash and newline.
bad1=`printf %03o \'\\\\`
bad2=`printf %03o \''
'`
e=
for i in 0 1 2 3; do
	for j in 0 1 2 3 4 5 6 7; do
		for k in 0 1 2 3 4 5 6 7; do
			case $i$j$k in
			000|$bad1|$bad2) continue ;;
			esac
			e="$e\\$i$j$k"
		done
	done
done
e=`printf "$e"`
[ "${#e}" = 253 ] || echo length bad

r1=`printf '%s\n' "$e" | { read -r x; printf '%s' "$x"; }`
[ "$r1" = "$e" ] || echo "read with -r bad"
r2=`printf '%s\n' "$e" | { read x; printf '%s' "$x"; }`
[ "$r2" = "$e" ] || echo "read without -r bad 1"
IFS=
r3=`printf '%s\n' "$e" | { read x; printf '%s' "$x"; }`
[ "$r3" = "$e" ] || echo "read without -r bad 2"