The difference between single bracket and double bracket in shell

The difference between brackets and double brackets

Single bracket test The command is to perform word separation on variables , When the variable value contains a white space character , To enclose variables in quotation marks ; And double bracketed test The command does not word separate variables .

[[email protected] ~]# name="hello"
[[email protected] ~]# [ $name = "hello" ]
[[email protected] ~]# echo $?
0
[[email protected] ~]# [[ $name = "hello" ]]
[[email protected] ~]