批处理文件未能设置变量，IF子句 [英] batch file fails to set variable in IF clause

问题描述

以下code未更新运行等于N为偶数虽然匹配发生。这意味着我没有落入CALL code。我思念的东西在这里？

  SET运行= YREM检查当前的文件日期/时间信息，并确定是否该文件已被present太长目录
REM跳过前4行作为标题信息不要求FOR / F令牌= 1-5 =跳过4 delims =%% G IN（'DIR / OD％SRCH_CRITERIA％'）DO（    ECHOPARAMS到processFile：%%摹%% ^ h %%我%% K
    IF %%ķ==。 （
        ECHOK：没有什么
        集中运行= N
        ECHO％运行％
    ）    IF %%满足K ==免费（
        ECHOK：FREE
        集中运行= N
        ECHO％运行％
    ）    ECHO％运行RUN％
    IF％运行％==Y（
        CALL：processFile%% G%% H我%%%% K
    ）
）
 

解决方案

您需要使用CMD.EXE的延迟扩展选项。

在你的脚本的顶部，放：

  SETLOCAL ENABLEEXTENSIONS enabledelayedexpansion
 

然后放：

  ENDLOCAL
 

在底部。

然后，你需要使用！快跑！而不是％运行％。

您code未工作的原因是，全部的FOR语句（包括其中的命令）的遭遇，当它被评估。这就是地步％运行％变量被扩展。

通过使用扩展推迟，你不展开它们，直到他们真正需要（你块中设置后，它们）。

您可以看到这个脚本的区别是：

 关闭@echo
SETLOCAL ENABLEEXTENSIONS enabledelayedexpansion设置XX = 0
为%%我在（A B C D）做（
    回声%%我
    集/一个XX = XX + 1
    如果％XX％== 3回声是正常的
    如果！XX！== 3回声是为延迟
）ENDLOCAL
 

它输出：

  A
b
C
是为延迟
ð
 

您会发现，与％XX％检查不起作用，因为这是评估当为声明开始（和 XX 为0）。延迟膨胀！XX！的确实的，因为这项工作是通过每次循环评估。

The following code is not updating Run to equal N even though the match occurs. this means I'm not dropping into the CALL code. Am i missing something here?

SET Run=Y

REM Check current files date/time information and establish if the file has been present too long in the directory
REM Skip first 4 lines as header information not required

FOR /f "tokens=1-5 skip=4 delims= " %%G IN ('dir /OD "%SRCH_CRITERIA% "') DO (

    ECHO "Params to processFile:  " %%G %%H %%I ""%%K""
    IF %%K.==.  ( 
        ECHO "K:nothing"
        SET Run=N
        ECHO %Run%
    ) 

    IF %%K==free (
        ECHO "K:FREE"
        SET Run=N
        ECHO %Run%
    ) 

    ECHO %Run% RUN
    IF %Run%=="Y" (
        CALL :processFile "%%G" "%%H" "%%I" "%%K"
    )   
)

解决方案

You need to use the delayed expansion option of cmd.exe.

At the top of your script, put:

setlocal enableextensions enabledelayedexpansion

and then put:

endlocal

at the bottom.

Then you need to use !Run! instead of %Run%.

The reason your code is not working is that the entire FOR statement (including the commands within it) is evaluated when it's encountered. That's the point where the %Run% variables are expanded.

By using deferred expansion, you don't expand them until they're actually needed (after you've set them within the block).

You can see the difference in this script:

@echo off
setlocal enableextensions enabledelayedexpansion

set xx=0
for %%i in (a b c d) do (
    echo %%i
    set /a "xx = xx + 1"
    if %xx%==3 echo yes for normal
    if !xx!==3 echo yes for delayed
)

endlocal

which outputs:

a
b
c
yes for delayed
d

You'll notice that the check with %xx% does not work because that was evaluated when the for statement started (and xx was 0). The delayed-expansion !xx! does work since that is evaluated each time through the loop.

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