测试批处理文件中的参数是否为空的正确方法是什么? [英] What is the proper way to test if a parameter is empty in a batch file?

问题描述

我需要测试是否设置了变量.我已经尝试了几种技术，但是当 %1 被引号包围时它们似乎都失败了，例如 %1 是 "c:some path带空格".

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.

根据本站，这些是支持的IF语法类型.所以，我没有办法做到这一点.

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

更新:在 2020 年 10 月 25 日，我将接受的答案从使用括号更新为使用波浪号.每个人都说波浪号更好，因为它更安全.我有点不明白，因为波浪号看起来更复杂，而且不太清楚它的用途是什么，但尽管如此，我还是改变了它.

UPDATE: on 2020-10-25, I updated the accepted answer from using brackets to using a tilde. Everyone says the tilde is better as it's more secure. I'm a little torn cause the tilde looks more complicated and is less clear as to what it's purpose is but nevertheless, I changed it.

推荐答案

您可以使用:

IF "%~1" == "" GOTO MyLabel

去除外部引号集.一般来说，这是比使用方括号更可靠的方法，因为即使变量中有空格它也能工作.

to strip the outer set of quotes. In general, this is a more reliable method than using square brackets because it will work even if the variable has spaces in it.

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