Windows echo 命令无法回显用户设置的变量
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Windows echo command can't echo a user-set variable
提问by jacobsee
What did I do to screw up my CMD shell? Windows XP Pro, open a cmd window and do:
我做了什么来搞砸我的 CMD 外壳？Windows XP Pro，打开一个 cmd 窗口并执行：
C:\>set tt = name
C:\>set tt
tt = name
C:\>echo %tt%
%tt%
C:\>echo %time%
14:13:28.67
The echo command doesn't work for some reason. I can echo the built-in variables just fine. Tried it on another computer and that works as expected
由于某种原因，echo 命令不起作用。我可以很好地回应内置变量。在另一台电脑上试过，效果如预期
回答by akf
The setcommand does not take spaces. The proper syntax would be:
该set命令不占用空格。正确的语法是：
set tt=name
What you have done in your example is set an environment variable tt<space>. With that in mind, you can try this:
您在示例中所做的是设置环境变量tt<space>。考虑到这一点，你可以试试这个：
echo %tt%
and see your output.
并查看您的输出。
回答by Eric
Have you tried setting the variable with no space between the equals? (set tt=name)
您是否尝试过在等号之间没有空格的情况下设置变量？（设置 tt=name）
回答by Franta
The most upvoted answer here, accepted far ago, claims that:
这里最受好评的答案，很久以前就被接受了，声称：
"The
setcommand does not take spaces."
“
set命令不占用空格。”
But that is not correct: The %tt %variable actually works: It can be set and referenced. (Despite it isconfusing.)
但这不正确：该%tt %变量实际上有效：它可以被设置和引用。（尽管它是混乱的。）
Problem reproduced:
问题重现：
Indeed, on my Win7:
确实，在我的 Win7 上：
C:\>set os
OS=Windows_NT
C:\>set tt = name
C:\>set tt2= name
C:\>set tt3=name
C:\>set tt
tt = name
tt2= name
tt3=name
I tried and got:
我尝试并得到：
C:\>echo "%os%"
"Windows_NT"
C:\>echo "%tt3%"
"name"
C:\>echo "%tt2%"
" name"
C:\>echo "%tt%"
"%tt%"
Resolved cases:
已解决案例：
The intuitively expected variable %tt%is not set. But %tt %is set instead:
%tt%未设置直观预期的变量。但是%tt %设置为：
C:\>echo "%tt %"
" name"
Even more, with a space at the end of the value, set tt4 = name :
更重要的是，在值的末尾有一个空格，set tt4 = name ：
C:\>echo "%tt4 %"
" name "
Conclusions:
结论：
The setcommand does not trim():
该set命令不会trim()：
- The space before "=" is included to the
var_name. - The space after "=" is included to the
var_value. - The space at the end of the
var_valueis included to it.
- “=”前的空格包含在
var_name. - “=”后的空格包含在
var_value. - 末尾的空格
var_value包含在其中。
On the other hand:
另一方面：
- The space at the beginning of the
var_nameis not included to it, which is rather normal for command line arguments in general.
- 开头的空格
var_name不包括在内，这对于一般的命令行参数来说是很正常的。
