mv \- move or rename files
moves (changes the name of)
has a mode which forbids writing,
reads the standard input to obtain a line;
refuses to move a file onto itself.
lie on different file systems,
must copy the file and delete the original.
In this case the owner name becomes
that of the copying process and any
linking relationship with other files
Directories may only be moved within the same parent
if the target exists and is not writable.