bash [[[a] == [a]]]不正确吗?方括号影响比较结果 [英] bash [[ [a] == [a] ]] not true? square bracket affect compare result

问题描述

有人知道为什么会这样吗?这是bash的错误吗?

Anyone know why this happens? Is this a bug of bash?

x='mnt:[4026532411]'

[[ $x == $x ]] && echo OK

我期望结果 OK ，但是没有.

I am expecting result OK, but it did not.

当然可以，

[[ "$x" == "$x" ]] && echo OK

但是据我所知，bash [[]]的优点是比较时无需引用var.

But as I know, bash [[ ]] have a merit that no need to quote var when compare.

x='a b'
[[ $x == $x ]] && echo OK

有效.

讽刺的事情是

x='mnt:[4026532411]'

[[ $x != $x ]] && echo Oh my god

结果是我的天哪

推荐答案

未引用的 == 和！= 的右侧被视为一种模式，而不是文字字符串. mnt:[4026532411] 将与 mnt:匹配，后跟精确的 one 分别为0、1、2、3、4、5或6，因为模式 mnt:[4026532411] 和 mnt:[0123456] 是等效的.要匹配字符串，您需要引用扩展名.

The unquoted right-hand side of == and != is treated as a pattern, not a literal string. mnt:[4026532411] will match mnt: followed by exactly one of 0, 1, 2, 3, 4, 5, or 6, since the patterns mnt:[4026532411] and mnt:[0123456] are equivalent. To match the lieral string, you need to quote the expansion.

x='mnt:[4026532411]'

[[ $x == "$x" ]] && echo OK

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