如何在 Bash 的复杂条件表达式中使用逻辑非运算符？
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How to use logical not operator in complex conditional expression in Bash?
提问by wiswit
I would like to have the logical not for the following condition expression in bash, how can I do this?
我想在 bash 中为以下条件表达式设置逻辑 not，我该怎么做？
if [[ $var==2 || $var==30 || $var==50 ]] ; then
do something
fi
how can I prepend the logical not directly in the above expression, it's very tedious to change it again into things like this:
如何在上面的表达式中不直接添加逻辑，再次将其更改为这样的内容非常繁琐：
if [[ $var!=2 && $var!=30 && $var==50 ]] ; then
do something
fi
thanks for any hints!
感谢您的任何提示！
回答by konsolebox
if ! [[ $var == 2 || $var == 30 || $var == 50 ]] ; then
do something
fi
Or:
或者：
if [[ ! ($var == 2 || $var == 30 || $var == 50) ]] ; then
do something
fi
And a good practice is to have spaces between your conditional operators and operands.
一个好的做法是在条件运算符和操作数之间留有空格。
Some could also suggest that if you're just comparing numbers, use an arithmetic operator instead, or just use (( )):
有些人还可能建议，如果您只是比较数字，请改用算术运算符，或者仅使用(( ))：
if ! [[ var -eq 2 || var -eq 30 || var -eq 50 ]] ; then
do something
fi
if ! (( var == 2 || var == 30 || var == 50 )) ; then
do something
fi
Although it's not commendable or caution is to be given if $varcould sometimes be not numeric or has no value or unset, since it could mean 0 as default or another value of another variable if it's a name of a variable.
尽管$var有时可能不是数字或没有值或未设置，这不是值得称赞或要注意的，因为它可能意味着 0 作为默认值或另一个变量的另一个值（如果它是变量的名称）。
