如何在 bash 脚本中使用正则表达式否定测试? [英] How do I negate a test with regular expressions in a bash script?

问题描述

使用 GNU bash(版本 4.0.35(1)-release (x86_64-suse-linux-gnu)，我想用正则表达式否定一个测试.例如，我想有条件地添加一个路径到PATH 变量，如果路径不存在，如:

Using GNU bash (version 4.0.35(1)-release (x86_64-suse-linux-gnu), I would like to negate a test with Regular Expressions. For example, I would like to conditionally add a path to the PATH variable, if the path is not already there, as in:

TEMP=/mnt/silo/bin
if [[ ${PATH} =~ ${TEMP} ]] ; then PATH=$PATH; else PATH=$PATH:$TEMP; fi
TEMP=/mnt/silo/Scripts:
if [[ ${PATH} =~ ${TEMP} ]] ; then PATH=$PATH; else PATH=$PATH:$TEMP; fi
TEMP=/mnt/silo/local/bin
if [[ ${PATH} =~ ${TEMP} ]] ; then PATH=$PATH; else PATH=$PATH:$TEMP; fi
export PATH

我确信有一百万种方法可以做到这一点，但我想知道是否可以以某种方式否定条件，例如(错误的):

I'm sure there are a million ways to do this, but what I would like to know is if the conditional can be negated somehow, as in (the erroneous):

TEMP=/mnt/silo/bin
if ![[ ${PATH} =~ ${TEMP} ]] ; then PATH=$PATH:$TEMP; fi
TEMP=/mnt/silo/Scripts:
if ![[ ${PATH} =~ ${TEMP} ]] ; then PATH=$PATH:$TEMP; fi
TEMP=/mnt/silo/local/bin
if ![[ ${PATH} =~ ${TEMP} ]] ; then PATH=$PATH:$TEMP; fi
export PATH

推荐答案

你没看错，只是在 ! 和 [[ 之间放一个空格，就像 >如果！[[

You had it right, just put a space between the ! and the [[ like if ! [[

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