a string judgment
![](http://dl2.iteye.com/upload/attachment/0126/9266/a01e6e4e-985f-35f3-9aa3-fad8fa9d60ba.png)
Two actual combat
[root@localhost ~]# name=fengji
[root@localhost ~]# [ -z $name ] && echo yes || echo no
no
[root@localhost ~]# name=""
[root@localhost ~]# [ -z $name ] && echo yes || echo no
yes
[root@localhost ~]# aa=11
[root@localhost ~]# bb=22
[root@localhost ~]# [ "$aa" == "$bb" ] && echo yes || echo no
no
[root@localhost ~]# [ "$aa" -eq "$bb" ] && echo yes || echo no
no
[root@localhost ~]# aa=22
[root@localhost ~]# [ "$aa" -eq "$bb" ] && echo yes || echo no
yes
[root@localhost ~]# [ "$aa" == "$bb" ] && echo yes || echo no
yes
Three multiple conditional judgments
![](http://dl2.iteye.com/upload/attachment/0126/9268/fe11601d-e123-322d-86d2-7872e708fa32.png)
Four actual combat
[root@localhost ~]# aa=22
[root@localhost ~]# [ -n "$aa" -a "$aa" -gt 33 ] && echo yes || echo no
no
[root@localhost ~]# [ -n "$aa" -a "$aa" -gt 3 ] && echo yes || echo no
yes