The command fuser lists which ``users'' or processes have
``files'' open. This is useful if you want to replace or remove a file
or unmount a file system without making enemies of fellow users. For
example,
% fuser -u data.in Is someone using data.in? data.in: 21064(hank) Yes hank is, the process is 21064.
Beware, fuser will not show if a user is editing a file since the editor copies the file to a buffer before editing.