Copy-then-remove-old has vastly different semantics. It creates a new file identity. For a start, just imagine what happens when the old file is still open from

Copy-then-remove-old has vastly different semantics. It creates a new file identity. For a start, just imagine what happens when the old file is still open from some processes. I'm not saying there should not be convenience wrappers taking the dangerous route. I'm saying there is no shell interface that fails gracefully if no safe operation is possible. Maybe mv should just get an -x flag, like GNU cp and other commands have.