全局变量在父、子shell中起作用

yinhaibo@yinhaibo-OptiPlex-9020:~$ m='hh'
yinhaibo@yinhaibo-OptiPlex-9020:~$ export m
yinhaibo@yinhaibo-OptiPlex-9020:~$ echo $m
hh
yinhaibo@yinhaibo-OptiPlex-9020:~$ sh
$ echo $m
hh
$ exit
yinhaibo@yinhaibo-OptiPlex-9020:~$ bash
yinhaibo@yinhaibo-OptiPlex-9020:~$ echo $m
hh
yinhaibo@yinhaibo-OptiPlex-9020:~$ exit
exit
yinhaibo@yinhaibo-OptiPlex-9020:~$ bash
yinhaibo@yinhaibo-OptiPlex-9020:~$ n='haha'
yinhaibo@yinhaibo-OptiPlex-9020:~$ export n
yinhaibo@yinhaibo-OptiPlex-9020:~$ echo $n
haha
yinhaibo@yinhaibo-OptiPlex-9020:~$ exit
exit
yinhaibo@yinhaibo-OptiPlex-9020:~$ echo $n

yinhaibo@yinhaibo-OptiPlex-9020:~$ bash
yinhaibo@yinhaibo-OptiPlex-9020:~$ n='haha'
yinhaibo@yinhaibo-OptiPlex-9020:~$ echo $n
haha
yinhaibo@yinhaibo-OptiPlex-9020:~$ sh
$ echo $n