Automatic save of .history in .cshrc

Hi!

I set the history to 8000:

   set history = 8000
   set savehist = (8000 merge)

I would like to move the first 4000 lines of .history to a directory. 
Let's call the directory ~/.history_archive.

The reason that I don't want to move all the contents of .history, is 
because I would like to have the recent history for auto completion.

I found out a csh script to partly do what I envisioned, from 
https://forums.freebsd.org/threads/csh-history-file.65582/:

   set HIST="~/.history"

   if (`wc --libxo text -l ${HIST} | cut -d '/' -f1` == 2000) then
         mv ${HIST} ${HIST}.old
         touch ${HIST} && chmod 600 ${HIST}
   endif

Would the following csh code be correct? Because csh only saves / 
appends to ~/.history when I log out, I use greater or equal to as the 
the condition. When there are 6000 lines or more, I split the .history 
files into two. The first one has 4000 lines, which will be moved to 
~/.history_archive, with a file name that contains time information. The 
other file is moved to be the current ~/.history.

   set HIST="~/.history"

   if (`wc --libxo text -l ${HIST} | cut -d '/' -f1` >= 6000) then

         split -l 4000 ${HIST}

         mv xaa ~/.history_archive/history-`date +"%Y-%m-%d-%H-%M" `

         mv xab ${HIST}

         chmod 600 ${HIST}
   endif

Cheers,

Xianwen