link 参考链接

GNU Bash Reference Manual 文档
https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Redirections

超详细的Shell中特殊字符的用法总结大全
https://www.51cto.com/article/600683.html

shell中各种括号的作用详解()、(())、[]、[[]]、{}
https://www.cnblogs.com/splendid/p/11201733.html

shell 脚本里的 特殊字符 $(( ))、$( )、``与${ }的区别
https://www.cnblogs.com/chenpython123/p/11052276.html

linux shell中'',""和``的区别
https://www.cnblogs.com/Skyar/p/5914942.html

【shell 中$() ，${}，${!},${#},$[] $(())，[ ] (( )) [[ ]]】
https://blog.csdn.net/qq_40003309/article/details/106907677?spm=1001.2101.3001.6650.2&utm_medium=distribute.pc_relevant.none-task-blog-2~default~CTRLIST~default-2.pc_relevant_aa&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2~default~CTRLIST~default-2.pc_relevant_aa&utm_relevant_index=5

${}和${}的用法
https://www.cnblogs.com/clark1990/p/16587282.html

Bash 中的特殊字符大全
https://www.cnblogs.com/duhuo/p/7133204.html

https://tldp.org/LDP/abs/html/index.html

Shell中特殊字符的用法总结大全
https://www.jb51.net/article/120595.htm

shell中的 ${x[@]} 、 ${#x[@]} 、 ${x[]} 、 ${#x[]} 数组
https://blog.csdn.net/qq_39677803/article/details/125147594

shell中的特殊符号总结
https://www.cnblogs.com/zhouhbing/p/4783147.html

shell 的 ${ }中 ##、%%、// 使用方法及举例
https://blog.csdn.net/llm_hao/article/details/126894676

【Shell 编程指南】shell中的(),{}几种语法用法
https://blog.csdn.net/qq_21438461/article/details/132930647