setting CLASSPATH of the jdbc jar file

hi all,
i am a newbie using jdbc interface to postgresql.
Information about the machine and pgsql server-
1. system: OS:Enterprise Lnux 4, Server:Apache2
2. PostgreSql 7.4.6

Please tell me that at which prompt(either as a root or postgres user) i
can set CLASSPATH. my jdbc jar file is in
/usr/share/java/pg74.215.jdbc3.jar. i tried as root as well as postgres
user and applied following command:
export CLASSPATH=/usr/share/java/pg74.215.jdbc3.jar:${CLASSPATH}
After that i looked it with "env" command.it looked well. but when i exit
and reenturned into root as well as postgres user and typed "env" i
couldnt see "CLASSPATH=/usr/share/java/pg74.215.jdbc3.jar".
please suggest how to set classpath and save it.
waiting anxiously
with regard mamoon.