fuser command examples

fuser – identify processes using files or sockets

Also see lsof which can be used to identify open files.

fuser -km /home

kills all processes accessing the file system /home in any way.

if fuser -s /dev/ttyS1; then :; else something; fi

invokes something if no other process is using /dev/ttyS1.

fuser telnet/tcp

shows all processes at the (local) TELNET port.