什么是正确的方法来测试变量在批处理文件中是否为空？ [英] What is the proper way to test if variable is empty in a batch file?

问题描述

我需要测试一个变量是否设置。我尝试了几种技巧，但是它们似乎在每当％1 被引号引起时失败，例如％1 是c：\ some path with spaces。

I need to test if a variable is set or not. I've tried several techniques but they seem to fail whenever %1 is surrounded by quotes such as the case when %1 is "c:\some path with spaces".

IF NOT %1 GOTO MyLabel // This is invalid syntax
IF "%1" == "" GOTO MyLabel // Works unless %1 has double quotes which fatally kills bat execution
IF %1 == GOTO MyLabel // Gives an unexpected GOTO error.

根据 this site ，这些是支持的 IF 语法类型。

According to this site, these are the supported IF syntax types. So, I don't see a way to do it.

IF [NOT] ERRORLEVEL number command
IF [NOT] string1==string2 command
IF [NOT] EXIST filename command

推荐答案

使用括号而不是引号：

IF [%1] == [] GOTO MyLabel

<sub>注意：原始答案是：

IF（％1）==（）GOTO MyLabel

@jeb指出这是不安全的，@Synetech建议一个替代方案，所以我修改了答案。</sub>

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