a=$(cat 1.sh)

等价于

a=`cat 1.sh`

而

a=(cat 1.sh) 相当于定义一个a数组，内容为cat 1.sh

a=(`cat 1.sh`)相当于把1.sh里面的内容当成a的数组，a仍旧是一个数组

a=$(`cat 1.sh`)此命令会报错，不能执行

 

[root@zejin240 chenzejin]# cat 1.sh hello world 2016 better [root@zejin240 chenzejin]# a=(cat 1.sh)[root@zejin240 chenzejin]# b=(`cat 1.sh`)[root@zejin240 chenzejin]# c=$(cat 1.sh)[root@zejin240 chenzejin]# d=`cat 1.sh` [root@zejin240 chenzejin]# echo ${a[@]}cat 1.sh[root@zejin240 chenzejin]# echo ${b[@]}hello world 2016 better[root@zejin240 chenzejin]# echo ${c[@]}hello world 2016 better[root@zejin240 chenzejin]# echo ${d[@]}hello world 2016 better [root@zejin240 chenzejin]# echo $acat[root@zejin240 chenzejin]# echo $bhello[root@zejin240 chenzejin]# echo $chello world 2016 better[root@zejin240 chenzejin]# echo $dhello world 2016 better [root@zejin240 chenzejin]# e=$(`cat 1.sh`) -bash: hello: command not found