8，shell 遍历字符串的字符

[root@centos7 ~]# cat a.txt 
abcdefg
[root@centos7 ~]# 
[root@centos7 ~]# sed -e 's#\(.\)#\1\n#g' a.txt 
a
b
c
d
e
f
g

[root@centos7 ~]# 
[root@centos7 ~]# cat a.txt|while read line ; do echo $line | sed -e 's#\(.\)#\1\n#g' ;done
a
b
c
d
e
f
g

[root@centos7 ~]#