Why does the for loop only display the state of echo? - China DOS Union Forum

Please see the following code (in a batch file):
-------------------------------------------
@echo off
FOR /L %%i in (1,1,3) do (
set /a T=%%
echo %T%)
pause>nul
--------------------------------------------
After the program runs, it does not appear as we predicted:
1
2
3
Instead:
ECHO is off.
........
What's going on and what's the solution?

────────────────　Moderation Record　────────────────
Performed by: namejm
Original title: Expert, come quickly for help
Current title: Why does the for loop only display the echo status?
Explanation: The original title was too vague, which was not conducive to forum search and management. After the moderator's prompt was issued three days ago, the original poster had not changed the title. Now I, on behalf of the helpless moderator, forcibly modified the title and deducted 4 points from the original poster (because the forum points rules have changed, and the punishment has been reduced appropriately).
────────────────　Moderation Record　────────────────

[ Last edited by namejm on 2006-10-19 at 01:09 ]

This is a problem of variable delay. In addition, it is found that the code of the original poster is wrong, set /a T=%%. The code modification is as follows:


@echo off 
setlocal enabledelayedexpansion
for /l %%i in (1,1,3) do ( 
    set T=%%i
    echo !T!
) 
pause>nul

Thanks, endless gratitude

Why use!T! here instead of %T%?

This involves the issue of environment variable delay. For a compound statement like this, cmd will preprocess the variables in the statement. Thus, %T% in the for statement will be replaced. And the variable %T% is not defined before the for, so echo %T% shows that echo is in a closed state.

To enable delayed environment variables is to prevent cmd from preprocessing environment variables in compound statements. Thus, the variable T can be displayed normally. Because environment variables are enabled, so change % to !...

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Here'stown共同成意义是什么说的是什么意义都公共意义});!T!的成意义是什么说的是什么意义都公共意义});!T!的
```
@echo off
FOR /L %%i in (1,1,3) do set a=%%i&call :1
pause>nul
goto :eof
:1
echo %a%
```

[ Last edited by qwe1234567 on 2006-10-3 at 22:05 ]

Wait, there seems to be some confusion in the input. Let's focus on the code part. The code you provided is a batch script. Here's the translation of the code part as is:

```
@echo off
FOR /L %%i in (1,1,3) do set a=%%i&call :1
pause>nul
goto :eof
:1
echo %a%
```

And the rest of the text that doesn't seem to be related to the code is a bit jumbled. But based on the requirements, we mainly handle the code part. So the translated content for the code part remains as above, and the other jumbled text is just as it is presented here. But actually, the correct way is to just output the relevant parts properly. Let's correct and present clearly:

The batch code part translated is:

```
@echo off
FOR /L %%i in (1,1,3) do set a=%%i&call :1
pause>nul
goto :eof
:1
echo %a%
```

And the edit information part remains as:

[ Last edited by qwe1234567 on 2006-10-3 at 22:05 ]

Floor1　pcl83	Posted 2006-10-03 09:44
初级用户　Posts 13　Credits 32
Please see the following code (in a batch file): ------------------------------------------- @echo off FOR /L %%i in (1,1,3) do ( set /a T=%% echo %T%) pause>nul -------------------------------------------- After the program runs, it does not appear as we predicted: 1 2 3 Instead: ECHO is off. ........ What's going on and what's the solution? ────────────────　Moderation Record　──────────────── Performed by: namejm Original title: Expert, come quickly for help Current title: Why does the for loop only display the echo status? Explanation: The original title was too vague, which was not conducive to forum search and management. After the moderator's prompt was issued three days ago, the original poster had not changed the title. Now I, on behalf of the helpless moderator, forcibly modified the title and deducted 4 points from the original poster (because the forum points rules have changed, and the punishment has been reduced appropriately). ────────────────　Moderation Record　──────────────── [ Last edited by namejm on 2006-10-19 at 01:09 ]

Floor2　pengfei	Posted 2006-10-03 09:47
银牌会员　Posts 485　Credits 1,218　From 湖南.娄底
This is a problem of variable delay. In addition, it is found that the code of the original poster is wrong, set /a T=%%. The code modification is as follows: @echo off setlocal enabledelayedexpansion for /l %%i in (1,1,3) do ( set T=%%i echo !T! ) pause>nul

Floor3　pcl83	Posted 2006-10-03 09:53
初级用户　Posts 13　Credits 32
Thanks, endless gratitude

Floor4　KIKOOOO	Posted 2006-10-03 10:01
初级用户　Posts 12　Credits 34
Why use!T! here instead of %T%?

Floor5　pengfei	Posted 2006-10-03 10:14
银牌会员　Posts 485　Credits 1,218　From 湖南.娄底
This involves the issue of environment variable delay. For a compound statement like this, cmd will preprocess the variables in the statement. Thus, %T% in the for statement will be replaced. And the variable %T% is not defined before the for, so echo %T% shows that echo is in a closed state. To enable delayed environment variables is to prevent cmd from preprocessing environment variables in compound statements. Thus, the variable T can be displayed normally. Because environment variables are enabled, so change % to !...

Floor6　无奈何	Posted 2006-10-03 10:51
荣誉版主　Posts 356　Credits 1,338
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Floor7　不得不爱	Posted 2006-10-03 21:58
超级版主　Posts 2,044　Credits 5,310　From 四川南充
Here'stown共同成意义是什么说的是什么意义都公共意义});!T!的成意义是什么说的是什么意义都公共意义});!T!的 ``` @echo off FOR /L %%i in (1,1,3) do set a=%%i&call :1 pause>nul goto :eof :1 echo %a% ``` [ Last edited by qwe1234567 on 2006-10-3 at 22:05 ] Wait, there seems to be some confusion in the input. Let's focus on the code part. The code you provided is a batch script. Here's the translation of the code part as is: ``` @echo off FOR /L %%i in (1,1,3) do set a=%%i&call :1 pause>nul goto :eof :1 echo %a% ``` And the rest of the text that doesn't seem to be related to the code is a bit jumbled. But based on the requirements, we mainly handle the code part. So the translated content for the code part remains as above, and the other jumbled text is just as it is presented here. But actually, the correct way is to just output the relevant parts properly. Let's correct and present clearly: The batch code part translated is: ``` @echo off FOR /L %%i in (1,1,3) do set a=%%i&call :1 pause>nul goto :eof :1 echo %a% ``` And the edit information part remains as: [ Last edited by qwe1234567 on 2006-10-3 at 22:05 ]