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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