China DOS Union

Maybe everyone knows, for those who don't know, let's learn.

It can also be used in other places.
::Without variable delay can also calculate @echo off for /f %%a in ('dir/b') do call :num_add file_num echo There are %file_num% files (folders) in the directory. pause goto :eof :num_add 　set/a %1+=1 　goto :eof

I don't know, learning.

Originally posted by HAT at 2008-6-24 22:36:
Don't know, learning.

Orz ……

This is also the role of call

(for /f %i in ('dir /b') do set /a n+=1 >nul)&call echo There are %n% files(folders) under the directory

The usage seen on the 4th floor is another new one I've encountered.

This is no different from the original poster's, just simplified a bit

But I'm a newbie, and I find such usage a bit strange and not very used to it. Still, I need to learn more from you all.

This kind of thing can't replace the delayed variable. They all display the final effect after completely ending a for + set loop, and can't use intermediate links at all. The role of the delayed variable is to use the intermediate results of set.

@echo off for /f %%a in ('dir/b') do ( call :num_add file_num echo %file_num% ) echo There are %file_num% files (folders) in the directory. pause goto :eof :num_add 　set/a %1+=1 　goto :eof

@echo off for /f %%i in ('dir /b') do ( set /a n+=1 >nul echo %n% ) echo There are %n% files (folders) in the directory pause

The above two are the same as the building owner and the above ppdos code, and can't use intermediate results.

@echo off setlocal enabledelayedexpansion for /f %%i in ('dir /b') do ( set /a n+=1 >nul echo !n! ) echo %n% pause

You can compare the results.

[ Last edited by metoo on 2008-6-25 at 07:26 PM ]

If you want to use the intermediate result, it's also okay.

(for /f "tokens=*" %i in ('dir /b') do set /a n+=1 >nul&call set _%n%=%i >nul)&call echo There are %n% files(folders) in the directory


echo %_9%

[ Last edited by PPdos on 2008-6-25 at 01:01 PM ]

This is a clever way. It uses consecutive multi-variable assignments respectively to obtain the value of one of the intermediate variables, rather than directly obtaining it through true consecutive assignment/intermediate links. It defines n variables to stepize the entire for loop, and these stepized results can only be used after the entire loop ends.

[ Last edited by metoo on 2008-6-25 at 08:42 PM ]

Originally posted by metoo at 2008-6-25 01:40 PM:
This is a clever way, which uses continuous multi-variable assignment respectively to obtain the value of one of the intermediate variables, rather than directly obtaining it through continuous assignment/intermediate links. It is to define n variables to...

Can the expert give an example?

Have everyone been talking for a long time and not realized that they are discussing around a very non-typical example? Doesn't anyone know that set /a has the default delay effect? The example of the LZ completely doesn't need variable delay or "intermediate results" and so on.
@echo off for /f %%a in ('dir/b') do set /a file_num+=1 echo There are %file_num% files (folders) under the directory %cd%.

- Just a beginner

Your approach is to obtain each step by "changing variables", which is to generate n different variables at one time. These variables can only be used after the for command has completely executed. This is what I call taking a shortcut. While delayed expansion allows using variables during the execution of the for command.

@echo off for /f "tokens=*" %%i in ('dir /b') do ( set /a n+=1 >nul call set _%n%=%%i >nul rem This sentence is actually problematic. Before the for is completed, %n% is empty, so all are setting the value of the _ variable echo %n% echo %_% echo %_1% rem The above 3 sentences are added by myself to verify whether the variables in the loop can be used ) echo\ echo\ echo\ ::New line ::By this point, the entire loop has ended, and the variables %n% and %_% take effect echo %_% echo %n% echo %_1% ::Verify that the %_1% variable does not exist echo\ echo\ echo\ ::New line ::The above 3 sentences are added by myself to verify whether the variables in the loop can be used call echo There are %n% files(folders) in the directory pause

[ Last edited by metoo on 2008-6-25 at 09:14 PM ]

Brother metoo's remarks on floor 9 are a bit thoughtless.

In the DOS era without variable delay, it is also possible to "assign continuously / directly obtain in the intermediate link".

This only needs to make some small changes to the :num_add section that is called.
And the scheme of using for + call instead of for + delay usually transfers all the loop body code to the called subroutine, and there are no restrictions inside the subroutine, where you can use it as you like.