regex - bash 中的@(...|...|...) 语法是什么？

Question

关注此 question 中提到的 @() 语法:

[[ $OSTYPE == *@(darwin|freebsd|solaris|cygwin|openbsd)* ]]

这个语法从何而来？为什么在这种情况下使用它？和 有什么区别:

[[ $OSTYPE =~ (darwin|freebsd|solaris|cygwin|openbsd) ]]

或

[[ $OSTYPE == *(darwin|freebsd|solaris|cygwin|openbsd) ]]

这一切似乎都是等价的。

是否使用此语法代替 =~ 运算符以提高正则表达式的可移植性？

谢谢你的解释

Answer 1

在 man bash 中搜索 extglob 选项:

If the extglob shell option is enabled using the shopt builtin, several extended pattern matching operators are recognized. In the following description, a pattern-list is a list of one or more patterns separated by a |. Composite patterns may be formed using one or more of the following sub-patterns:

?(pattern-list)
    Matches zero or one occurrence of the given patterns
*(pattern-list)
    Matches zero or more occurrences of the given patterns
+(pattern-list)
    Matches one or more occurrences of the given patterns
@(pattern-list)
    Matches one of the given patterns
!(pattern-list)
    Matches anything except one of the given patterns