Windows批处理文件不输出变量

Question

我有一个批处理文件来创建每周备份。我创建了一个名为mydate的变量，我用它来格式化输出文件夹和回显日志。当我运行批处理并将每一行重定向到日志文件时，它可以正常工作：

set mydate=%date:~10,4%-%date:~4,2%-%date:~7,2%
echo My Date is %mydate% >>TestEchoLog.txt
echo Backup triggered at %mydate% >>TestEchoLog.txt

Cmd窗口：

D:\>set mydate=2017-06-26
D:\>echo My Date is 2017-06-26  1>>TestEchoLog.txt
D:\>echo Backup triggered at 2017-06-26   1>>TestEchoLog.txt

TestEchoLog.txt：

My Date is 2017-06-26 
Backup triggered at 2017-06-26

但是，如果我将命令包装到单个重定向中，我的变量就会停止工作：

>>TestEchoLog.txt (
set mydate=%date:~10,4%-%date:~4,2%-%date:~7,2%
echo My Date is %mydate% 
echo Backup triggered at %mydate% 

Cmd窗口：

D:\>(
set mydate=2017-06-26
 echo My Date is
 echo Backup triggered at
) 1>>TestEchoLog.txt

TestEchoLog.txt：

My Date is  
Backup triggered at  

我该如何解决这个问题？显然，一种解决方法是在每一行上都有重定向，但这是一个足够长的指令集，我宁愿不这样做。

谢谢！

Answer 1

设置变量，然后将其回显到文件中：

set mydate=%date:~10,4%-%date:~4,2%-%date:~7,2%
(
echo My Date is %mydate% 
echo Backup triggered at %mydate%
)>>TestEchoLog.txt