[root@localhost ~]# mkdir dy
[root@localhost ~]# cd dy
[root@localhost dy]# touch dzp dzp2 dzp3 dzp34 dzpcang dzpbols
[root@localhost dy]# ls
dzp dzp2 dzp3 dzp34 dzpbols dzpcang
[root@localhost dy]# la dzp
bash: la: command not found...
[root@localhost dy]# ls dzp
dzp
[root@localhost dy]# ls dzp*
dzp dzp2 dzp3 dzp34 dzpbols dzpcang
[root@localhost dy]# ls dzp?
dzp2 dzp3
[root@localhost dy]# ls dzp[0-9]
dzp2 dzp3
[root@localhost dy]# ls dzp[0-9][0-9]
dzp34
[root@localhost dy]# ls dzp[^0-9]
ls: cannot access dzp[^0-9]: No such file or directory
[root@localhost dy]# touch dzpa
[root@localhost dy]# ls dzp[^0-9]
dzpa
[root@localhost dy]# ls dzp[^0-9]*
dzpa dzpbols dzpcang

[root@localhost dy]# echo ls
ls
[root@localhost dy]# echo dzp
dzp
[root@localhost dy]# aa=123
[root@localhost dy]# echo $aa
123
[root@localhost dy]# echo '$aa'
$aa
[root@localhost dy]# echo "$aa"
123
[root@localhost dy]# aa=ls
[root@localhost dy]# echo "$aa"
ls
[root@localhost dy]# aa=`ls`
[root@localhost dy]# echo "$aa"
dzp
dzp2
dzp3
dzp34
dzpa
dzpbols
dzpcang
[root@localhost dy]# bb=$(ls)
[root@localhost dy]# echo $bb
dzp dzp2 dzp3 dzp34 dzpa dzpbols dzpcang
[root@localhost dy]# echo $(date)
Sat Jul 15 17:23:31 CST 2017
[root@localhost dy]# echo \$bb
$bb