cat
while read -r l; do echo "$l"; done <

cat -n
while read -r l; do echo "$l"$; done <

cat -e
n=0; while read -r l; do n="$((n+1))" printf ' %d %s\n' "$n" "$l"; done <

cat -b
n=0; while read -r l; do [ -n "$l" ] && n="$((n+1))" && printf ' %d %s' "$n" "$l"; echo; done <