Shell脚本中‘‘ () {} [] " " [[]] ``的不同用法

[[]]在脚本的使用中作用一是来匹配扩展正则表达式用法[[ =~ ]]例如：

[[email?protected] data]# touch f1.sh
[[email?protected] data]# file=f1.sh ;[[ $file =~ .sh$ ]]
[[email?protected] data]# echo $?
0
[[email?protected] data]# file=f1.shsh ;[[ $file =~ .sh$ ]]
[[email?protected] data]# echo $?
1

[[]]在脚本中的作用二是来匹配通配符用法：[[ == ]]或[[ != ]]例如：

[[email?protected] script]# file=f1.shsh
[[email?protected] script]# [[ "$file" == f ]]
[[email?protected] script]# echo $?
0
[[email?protected] script]# [[ "$file" == fx ]]
[[email?protected] script]# echo $?
1

[[email?protected] script]# ( u=1;sleep 1000 )