中国DOS联盟

RE qzwqzw:

It has been corrected. However, this "character acts to cancel the special uses for other special symbols (such as ^, &, |). So it feels safer to add a pair of "" when using the set /a command. Hehe.

Good stuff, thanks to the楼主. I have downloaded it as a DOC document and printed it for study.

:lol:

This is indeed a very valuable article, which is quite helpful for understanding cmd.

ok

Ask about this:

! !
① When variable delay is enabled, enclosing the variable name with !! means referring to the variable value.
I enabled variable delay and used !! to reference the variable, but it didn't work.
Is there any other condition needed?

I'm relatively stupid, please forgive me.

Re flamemperor:

Did you start with Setlocal EnableDelayedExpansion?

Please post your code for us to see?

Thanks to the moderator for replying. I've already solved the problem. It was my own mistake. Thank you. Now I'm still a bit confused about variable delays, and I'll keep learning.

What else is there to say! Just top it first

Learned it

I've always read posts without replying in cn-dos. Seeing this great post, I think I need to change my bad habit.

Non-sense thanks to version master lxmxn
Benefited a lot!!!

Just happened to not understand, it helped me a lot

The `^` is an escape character. In a batch file, the `|` is a special character that has a specific meaning (pipeline operation). When using `|` inside a `for /f` command, it needs to be escaped with `^` so that the shell interprets it correctly as part of the command being passed to `find /i "Physical Address"` rather than as a special operator within the batch file's syntax itself.

So the translated text remains as the original batch code part:
```
for /f "tokens=2 delims=:" %%a in ('ipconfig /all^|find /i "Physical Address"') do echo %%a>c:\MAC.txt
问题来了，'ipconfig /all^|find /i "Physical Address"'
既然是让 'ipconfig /all传输给下一个命令 为什么又用^这个符号来取消|的作用呢？
如果只运行'ipconfig /all^|find /i "Physical Address
可以不需要这个符号
为什么在for 里面一定要加上^
```

RE qdloverr:

for /f "tokens=2 delims=:" %%a in ('ipconfig /all^|find /i "Physical Address"') do echo %%a>c:\MAC.txt

If you don't add ^ before | between ipconfig /all and find, this statement can be understood as:
for /f "tokens=2 delims=:" %%a in ('ipconfig /all is passed to find /i "Physical Address"') do echo %%a>c:\MAC.txt, which obviously leads to a syntax error. This may be caused because the priority of the pipe symbol (|) is higher than the parentheses () after in in the for command.

If you don't add ^, to make ipconfig /all|find /i "Physical Address" a whole, maybe it can be like this:

for /f "tokens=2 delims=:" %%a in (' "ipconfig /all|find /i "Physical Address" "') do echo %%a>c:\MAC.txt

Last edited by lxmxn on 2007-10-7 at 06:03 PM ]