批处理 - 如何回声%%变量%% [英] Batch - How to Echo %%Variable%%

问题描述

我有一个小问题，我工作的一个批处理文件。

I have a small problem with a batch file I'm working on.

下面是一个简单的例子：

Here's a simple sample:

我想获得字符串有为我的结果。
但结果我得到的仅仅是HELLO

I would like to get the string "THERE" as my result. But the result I get is just "HELLO"

set hello=there
set a=h
set b=ello 
set result=%a%%b%
echo %result%

我已经尝试过这样的事情：

I already tried something like this:

Echo %%result%%

和可悲的是，它只是让我的结果HELLO％％
任何帮助将是巨大的。谢谢！

And Sadly, it just gets me the result %HELLO% Any help would be great. Thanks!

推荐答案

之所以 %%结果%% 为您提供％结果％在输出的是， %% 标记是相互preTED的首先，的进一步间pretation不这样做。

The reason that %%result%% gives you %result% on the output is that the %% tokens are interpreted first, and further interpretation is not done.

不过，你可以用它来你的优势，做一个的第二的有以下伎俩间接的级别：

However, you can use that to your advantage, doing a second level of indirection with the following trick:

@echo off
set result=hello
echo %result%
call :iset second %%result%%
echo %second%
goto :eof

:iset
    for /F "usebackq tokens=*" %%i in (`echo %%%2%%`) do set %1=%%i
    goto :eof

秘密在于传递东西你要跨preTED（在这种情况下， %%结果%% 通过在文字 ％结果％按照第一款规定的规则，的不的它的内部pretation）。

The secret lies in passing the thing you want interpreted (in this case, %%result%% passes in the literal %result% as per the rules stated in the first paragraph, not the interpretation of it).

的为循环再回波的（你好）包围的相互pretation ％...％（同​​样，双 %% 减少了％），这样的是的也是跨preTED，它使用了设置你也通过了目标变量。

The for loop then echos the interpretation of that (hello) surrounded by %...% (again, the double %% reduces to %), so that it is also interpreted, and it uses that to set the target variable you also passed in.

其结果是，它有效地为您提供：

The upshot is that it effectively gives you:

%(%result%)%

这就是你追求的。

which is what you're after.

不过也许我建议，你开始寻找到PowerShell的，这样你就不必执行的将来，这些批次体操： - ）

Might I suggest, however, that you start looking into Powershell, so that you don't have to perform these batch-gymnastics in future :-)

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