=~ 是什么意思？

Question

遇到一个 shell 脚本，其中条件语句中有“=~”，我想知道它是什么意思。在 Google 或 SO 网站上运气不佳。

例子：

if [[ $VAR =~ 'this string' ]]

Answer 1

它是一个正则表达式匹配运算符。

从bash手册页：

An additional binary operator, =~, is available, with the same
precedence as == and !=.  When it is used, the string to the
right of the operator is considered an extended regular
expression and matched accordingly (as in regex(3)).  The return
value is 0 if the string matches the pattern, and 1 otherwise.

有关更多详细信息，请参阅bash的手册页（搜索=~）