如何在bash脚本中使用正则表达式对测试求反? [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)-发行版(x86_64-suse-linux-gnu))，我想使用正则表达式取消测试.例如，我想有条件地向PATH变量(如果路径尚不存在)，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

我敢肯定有百万种方法可以做到这一点，但是我想知道的是，是否可以以某种方式否定条件，如(错误的)中所示:

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

您说对了，只需在!和[[之间放置一个空格，如if ! [[

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

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