awk 统计域出现的次数并且排序

[root@VM_166_163_centos ~]# cat 1
a
a
a
b
b
b
d
e
e
s
x
d
s
s
c
s
d
x
c
s
d
s
x
f
d
d

[root@VM_166_163_centos ~]# awk '{num[$1]++} END{for(k in num)print k,"----",num[k]|"sort -rk 2"}' 1
s ---- 6
d ---- 6
x ---- 3
b ---- 3
a ---- 3
e ---- 2
c ---- 2
f ---- 1

[root@VM_166_163_centos ~]# awk '{num[$1]++} END{for(k in num)print k,"----",num[k]|"sort -k 2"}' 1
f ---- 1
c ---- 2
e ---- 2
a ---- 3
b ---- 3
x ---- 3
d ---- 6
s ---- 6

[root@VM_166_163_centos ~]# awk '{num[$1]++} END{for(k in num)print k,"----",num[k]|"sort -k 2"}' 1 | head -n 3
f ---- 1
c ---- 2
e ---- 2