aix-oracle中的profile中的export是什么意思？

redandblack

ORACLE_BASE=/oracle/app/oracle; export ORACLE_BASE
ORACLE_HOME=$ORACLE_BASE/product/9.2.0; export ORACLE_HOME
ORACLE_SID=zygl; export ORACLE_SID
LD_LIBRARY_PATH=$ORACLE_HOME/libORACLE_HOME/network/lib; export LD_LIBRARY_PAT
H
LIBPATH=$ORACLE_HOME/lib; export LIBPATH
NLS_LANG=AMERICAN_AMERICA.ZHS16GBK; export NLS_LANG
ORA_NLS33=$ORACLE_HOME/ocommon/nls/admin/data; export ORA_NLS33
PATH=/usr/ccs/binORACLE_HOME/binPATH;export PATH
PATH=$ORACLE_BASE/OPatchPATH;export PATH
#DISPLAY=localhost:0.0; export DISPLAY
umask 022
set -o vi

sshd

Any exported variable will be seen by all sub shells

example:

1 oracle@suse8:/home/oracle>; X=x
2 oracle@suse8:/home/oracle>; bash
3 oracle@suse8:/home/oracle>; echo $X

4 oracle@suse8:/home/oracle>; exit
exit
5 oracle@suse8:/home/oracle>; export X=x
6 oracle@suse8:/home/oracle>; bash
7 oracle@suse8:/home/oracle>; echo $X
x
8 oracle@suse8:/home/oracle>; exit
exit

1. set up a shell variable X to have value x
2. enter a sub shell
3. X has no vaule in the sub shell
4. exit the sub shell

5. setup a environment variable X
6. enter a sub shell
7. X has value x in the sub shell
8. exit the sub shell

redandblack

不明白，能具体解释一下吗？