export使在父shell中定义的环境变量在子shell中仍然有效。
eg：
[oracle@ora10g ~]$ echo $AA [oracle@ora10g ~]$ echo $BB [oracle@ora10g ~]$ AA=aaa [oracle@ora10g ~]$ BB=bbb [oracle@ora10g ~]$ export BB [oracle@ora10g ~]$ bash [oracle@ora10g ~]$ echo $AA [oracle@ora10g ~]$ echo $BB bbb [oracle@ora10g ~]$ exit exit [oracle@ora10g ~]$ echo $AA aaa [oracle@ora10g ~]$ echo $BB bbb [oracle@ora10g ~]$
