Windows XP批处理文件连接
我正在尝试完成以下荒谬的任务：
我有一个包含一组完全限定的文件名的文本文件。我想迭代该文件并将每一行附加到一个公共变量，该变量可以传递给命令行工具。例如，该文件可能是：
C:\dir\test.txt
C:\WINDOWS\test2.txt
C:\text3.txt
我想将它们分配给某个变量“a”，这样：
a = "C:\dir\test.txt C:\WINDOWS\test2.txt C:\text2.txt"
第二个问题是 - 什么是好的批处理文件参考？我在 Windows 材料和许多本土网站中找到了一些东西，但没有什么特别完整的。
I'm trying to accomplish the following ridiculous task:
I have a text file containing a set of fully qualified filesnames. I want to iterate through the file and append each line to a common variable, that can be passed to a command line tool. For example, the file might be:
C:\dir\test.txt
C:\WINDOWS\test2.txt
C:\text3.txt
and I'd like to assign them to some variable 'a' such that:
a = "C:\dir\test.txt C:\WINDOWS\test2.txt C:\text2.txt"
A secondary question is - what is a good batch file reference? I'm finding some stuff in the Windows material, and a lot of home-grown websites, but nothing particularly complete.
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至于参考，SS64.com 还不错。 Rob van der Woude 也经常被链接。
至于您的问题，这很简单：
更深入的解释：
我们在这里启用延迟扩展。这一点至关重要，否则我们将无法在随后的
for循环中操作文件列表。for /f迭代文件中的行，这正是我们所需要的。在每次循环迭代中，我们将下一行附加到LIST变量中。请注意使用!LIST!而不是通常的%LIST%。这表示延迟扩展并确保每次运行此命令时都会重新评估变量。通常，一旦读取并解析了一行，
cmd就会将变量扩展为它们的值。对于cmd来说，单行要么是一行，要么是算作的所有内容，这恰好适用于由括号分隔的块，就像我们在这里使用的那样。因此，对于 cmd 来说，完整的块是一个单独的语句，无论循环内部运行的频率如何，它都会被读取和解析一次。如果我们在这里使用
%LIST%而不是!LIST!，那么该变量将立即被其值替换（此时为空），并且循环将具有看起来像这样：显然这不是我们想要的。延迟扩展可确保仅在真正需要变量值时才扩展变量。在这种情况下，当循环内部运行并构造文件名列表时。
之后，变量
%LIST%或!LIST!（现在使用哪个已经不再重要）包含文件中的行列表。有趣的是，
set命令的帮助正是包含这个延迟扩展的示例：As for references, SS64.com isn't bad. Rob van der Woude gets linked fairly often, too.
As for your problem, that's easy:
More in-depth explanation:
We're enabling delayed expansion here. This is crucial as otherwise we wouldn't be able to manipulate the list of files within the
forloop that follows.for /fiterates over lines in a file, so exactly what we need here. In each loop iteration we append the next line to theLISTvariable. Note the use of!LIST!instead of the usual%LIST%. This signals delayed expansion and ensures that the variable gets re-evaluated every time this command is run.Usually
cmdexpands variables to their values as soon as a line is read and parsed. Forcmda single line is either a line or everything that counts as a line, which happens to hold true for blocks delimited by parentheses like the one we used here. So forcmdthe complete block is a single statement which gets read and parsed once, regardless of how often the interior of the loop runs.If we would have used
%LIST%here instead of!LIST!then the variable would have been replaced immediately by its value (empty at that point) and the loop would have looked like this:Clearly this isn't what we wanted. Delayed expansion makes sure that a variable is expanded only when its value is really needed. In this case when the interior of the loop runs and constructs a list of file names.
Afterwards the variable
%LIST%or!LIST!(now it doesn't really matter anymore which to use) contains the list of lines from the file.Funnily enough, the help for the
setcommand includes exactly this example for delayed expansion:您可以使用 FOR /F 命令来完成您想要的操作。
这是我多次使用的好资源：
http://www.robvanderwoude.com/batchfiles.php
What you're after can be done with a FOR /F command.
Here's a good resource I've used many times:
http://www.robvanderwoude.com/batchfiles.php
一本好书：Tim Hill 的《Windows NT Shell 脚本》。我的版本是 1998 年发布的，但它对于 Windows 2008 中的 Windows 命令程序仍然有效。
A good book: Windows NT Shell Scripting by Tim Hill. The edition I have was published in 1998 but it is still valid for Windows command programs in Windows 2008.
操作系统：Windows Server 2003
OS: WINDOWS SERVER 2003