lockf - lock files from within shell-scripts (used by sn news system)

lockf  can  be  used  to lock files from within shell-scripts. Filedescriptor 3 is always locked, and the
       lock remains until the process is killed.  The process-id is written to standard output, as to facilitate
       killing the process.

       It is used by the sn news system.

       lockf - lock files from within shell-scripts (used by sn news system)

sn(8)lockf(8)

lockf