Bash布尔测试 [英] Bash Boolean testing
问题描述
如果一个标志设置为true，另一个标志设置为false，我正在尝试运行代码块.即
I am attempting to run a block of code if one flag is set to true and the other is set to false. ie
var1=true
var2=false
if [[ $var1 && ! $var2 ]]; then var2="something"; fi
由于无法评估我所期望的方式，因此我编写了其他几个测试用例，并且很难理解如何评估它们.
Since that did not evaluate the way that I expected I wrote several other test cases and I am having a hard time understanding how they are being evaluated.
aa=true
bb=false
cc="python"
if [[ "$aa" ]]; then echo "Test0" ; fi
if [[ "$bb" ]]; then echo "Test0.1" ; fi
if [[ !"$aa" ]]; then echo "Test0.2" ; fi
if [[ ! "$aa" ]]; then echo "Test0.3" ; fi
if [[ "$aa" && ! "$bb" ]]; then echo "Test1" ; fi
if [[ "$aa" && ! "$aa" ]]; then echo "Test2" ; fi
if [[ "$aa" ]] && ! [[ "$bb" ]]; then echo "test3" ; fi
if [[ "$aa" ]] && ! [[ "$cc" ]]; then echo "test4" ; fi
if [[ $aa && ! $bb ]]; then echo "Test5" ; fi
if [[ $aa && ! $aa ]]; then echo "Test6" ; fi
if [[ $aa ]] && ! [[ $bb ]]; then echo "test7" ; fi
if [[ $aa ]] && ! [[ $cc ]]; then echo "test8" ; fi
当我运行前面的代码块时，我得到的唯一输出是
When I run the preceding codeblock the only output I get is
Test0
Test0.1
Test0.2
Test0
Test0.1
Test0.2
但是，我的期望是我会得到
however, my expectation is that I would get
Test0
测试1
Test3
Test5
Test7
Test0
Test1
Test3
Test5
Test7
我试图了解运行类似测试的最佳方法，但是我发现的大多数示例都以
的格式设置如果[["$ aa" == true]];
这不是我想做的.因此，我的问题是进行这种比较的最佳方法是什么?为什么我希望通过的几个测试用例根本不会通过?
I have tried to understand the best way to run similar tests, however most examples I have found are set up in the format of
if [[ "$aa" == true ]];
which is not quite what I want to do. So my question is what is the best way to make comparisons like this, and why do several of the test cases that I would expect to pass simply not?
谢谢！
推荐答案
没有任何运算符， [[]仅检查变量是否为空.如果是，则将其视为错误，否则将其视为正确.变量的内容无关紧要.
Without any operators, [[ only checks if the variable is empty. If it is, then it is considered false, otherwise it is considered true. The contents of the variables do not matter.
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