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Bash Case语句的终结符

 3 years ago
source link: https://www.lujun9972.win/blog/2019/07/01/bash-case%E8%AF%AD%E5%8F%A5%E7%9A%84%E7%BB%88%E7%BB%93%E7%AC%A6/index.html
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Bash Case语句的终结符

Case分支语句的一般常用格式是这样的: 

case $变量名 in
    模式1)
        命令序列1
        ;;
    模式2)
        命令序列2
        ;;
    *)
        默认执行的命令序列
        ;;
esac

但是今天偶尔看到 bash manual 中关于 case 语句的说明中有这么一段: 

If the ;; operator is used, no subsequent matches are attempted after the first pattern  match.
Using  ;&  in  place of ;; causes execution to continue with the list associated with the next set of  patterns.
Using  ;;&  in place  of  ;;  causes the shell to test the next pattern list in the statement, if any, and execute any associated list on a successful  match.

也就是说，case语句的分句终止符不仅仅可以时 ;; 还可以 ;& 和 ;;&, 他们的作用分别为:

;;不再进行后续的匹配，直接跳出case语句 ;&不再进行后续的匹配，继续执行后面的case分句 ;;&继续对后面的case分句进行匹配，若能找到匹配项则执行该分句。


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