Synopsis:
   flush

Description:
   This discards any data pending in the client's hold buffer when HOLD_MODE
   is on (and HOLD_MODE is then turned off).  This includes server messages,
   and messages generated internally by the client (such as by NOTIFY).  The
   client then discards all server messages received, until one full second
   passes without receiving anything from the server.  It is most useful for
   flushing server output from commands that generate a lengthy reply, such
   as LINKS or LIST or WHO.

See Also:
   set(4) hold_mode

Other Notes:
   FLUSH is a blocking command (meaning the client can't do anything until
   the command is done), so it may cause the client to ping timeout from
   your server.  It does not actually tell the server to stop sending data.