If u want, than each sqlplus user have anything special in command promt u should:

-- use glogin.sql file for setup prompt line
-- use query that can get machine name and OS user name from session
for example:
select SID,OSUSER,MACHINE from v$session where sid = ( select distinct sid from v$mystat );
...

and then:

col v_r new_value prt noprint;
select '['||rtrim(OSUSER)||'@'||rtrim(MACHINE)||']SQL>' v_r from v$session where sid = ( select distinct sid from v$mystat );
set sqlprompt &prt;

I tried this script, it works.