shell------打印出文档中只含有一个数字的行

#!/bin/bash
for i in `cat /root/passwd` ;do
n=`echo $i |sed 's/[^0-9]//g'|wc -c`
#echo $n
if [ $n -eq 2 ];then
echo $i
else
continue
fi
done

[root@ceshi ~]# cat passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
fahsdjkljfsda;j5skjdlaf
sdfavcxxcv34fd
sdfa2sdafvcx
[root@ceshi ~]# sh 2.sh
fahsdjkljfsda;j5skjdlaf
sdfa2sdafvcx
[root@ceshi ~]#