Shell中if的格式：

 

if  [ conditions ]

    then

           expr

elif [ conditions ]

    then

           expr

else

fi

 

 [ conditions ] 包括

1. !,-a,-o

2. -n,-z, =,!= 

3. -eq,-ge,-gt,-le,-lt,-ne 

4. -ef,-nt,-ot 

5. -b,-c,-d,-e,-f,-g,-G,-h, -k,-L,-O,-p,-r,-s,-S,-t,-u,-w,-x

 

类型1为逻辑判断 是、非、与或

[root@021Y-SH-BKAP ~]# if [ 1=1 -a 2=2 -o 2=3 ] ; then echo $? ;fi

0
这个逻辑就是同时满足1=1和2=2条件为真，或2=3条件为真，显然或前面已经满足，所以返回的结果为0

2