Lsof (LiSt Open Files) lists information about files that are open by the
running processes.  An open file may be a regular file, a directory, a block
special file, a character special file, an executing text reference, a
library, a stream or a network file (Internet socket, NFS file or Unix domain
socket).

See also fstat(1) in the base system.

WWW: http://www-rcd.cc.purdue.edu/~abe/