[root@mail ~]# cat aa.txt
hahahaha
aaaaaaa
aaaaaaa
bbbbbbbbbbbbb
vvvvvvvv
ddddddddd
vvvvvvvv
aaaaaaa
bbbbbbbbbbbbb
ddddddddddd
$
#
345
345
a5^
[root@mail ~]# sed -n '/[a-zA-Z0-9@#$%^&*]/!=' aa.txt
4


[root@mail ~]# grep -n ^$ aa.txt    (感谢soulmate)
4:
 

[root@mail ~]# awk '/^$/{print NR}' aa.txt  (感谢继续飞翔)
4

 

[root@mail ~]# sed -n '/^$/=' aa.txt      (感谢继续飞翔)
4