尝试理解这段代码（批处理，CMD）

Question

尝试理解这段代码（批处理，CMD）

4

    @echo off
setlocal enabledelayedexpansion
::just a sample adapter here:
set "adapter=Ethernet adapter Local Area Connection"
set adapterfound=false
echo Network Connection Test
for /f "usebackq tokens=1-2 delims=:" %%f in (`ipconfig /all`) do 
(
    set "item=%%f"
    if /i "!item!"=="!adapter!" 
  (
        set adapterfound=true
      )
   else if not "!item!"=="!item:IP Address=!" if "!adapterfound!"=="true" 
  (
        echo Your IP Address is: %%g
        set adapterfound=false
      )
)

我对batch很陌生，请问以下几个问题:

在这种情况下，setlocal enabledelayedexpansion是什么作用?
usebackq是什么意思? (我尝试过查找但没有完全理解)
变量%%g是如何初始化的，并且它是全局还是局部的?

谢谢您的时间!

- user7253664

实际上，脚本无法工作，因为存在一些语法错误：for ... do (，if ... (，) else（括号不能单独放在一行中！） - aschipfl

1

我建议阅读Stack Overflow批处理文件文档页面。 - SomethingDark

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- user6597761 · Accepted Answer

Delayed Expansion will cause variables to be expanded at execution time rather than at parse time.
Code below would seem to echo second second, but it prints first second instead.
```
 setlocal EnableDelayedExpansion
 set var=first
 set var=second & Echo %var% !var!
```
Source: SS64
usebackq forces for loops use backquotes (`dir`) to evaluate the commands inside it and use the output for the forloop, instead of open a file. This will list all elements of Documents predeced with an asterisk.
```
echo Documents:
for /f "usebackq" %%i in (`dir /b "C:\Users\%username%\Documents\"`) do (
  echo * %%i
)
pause
```
They're local. Using the previous example, %%iis defined just in the for loop, no additional initialization needed.