A Capital S in ls -l Means Your setuid Bit Is Doing Nothing

Run chmod 4655 file and ls -l prints -rwSr-xr-x — the capital S means setuid is set but dead, because the owner has no execute bit. Most online chmod calculators render it as lowercase s and never warn you. This one gets S/T right and parses symbolic syntax like u+x,go-w that almost no competitor touches.