[ This can be considered step 2 of my previous question Is it possible to change GNU screen 
session name after created? ]
Actually, I'd like to write a script that can display current screen 
session name and change current 
session name.
For example:
sren armcross
It will change the 
session name to armcross (ARM gcc cross compiler) and output something like:
screen 
session name changed from '25278.pts-15.linux-ic37' to 'armcross'
So, the key question now is how to get current 
session name. Not only for display the old 
session name, but according to Is it possible to change GNU screen 
session name after created? , I have to know it(pass to -d -r) before I can change it to something else.
Can we use $STY for current 
session name? No. $STY will not change after you have changed the 
session name to a user-defined one. However, for command 
screen -d -r <oldsessname> -X sessionname armcross
 should be the user-defined name(if ever defined) instead of $STY, otherwise, screen spouts error "No screen session found."
Maybe, there is a verbose way, use screen -list to list all sessions(user-defined name listed), then, match the pid part from $STY against those listed sessions and we will find current session's user-defined name. It should not be so verbose for such a straightforward question. Don't you think so?
The -d -D and -r -R options seems to expose too much implementation detail to screen's user. It seems, to rename a session, you have to detach it, then do the rename, then reattach it. Right?
My env: opensuse 11.3, GNU screen 4.00.03 (FAU) 23-Oct-06
Thank you.