China DOS Union

A post that's 34 screens long~~ sigh~~

bagpipe, I don't know whether you noticed it, but I found there's a trick in this:

:exec
%*
goto :eof

But I still can't quite make sense of it for now. Heh. We'll have to ask willsort and the other three moderators for a deeper explanation.


Also, to willsort:
I think the following code isn't much less efficient than what we discussed before here:a question about randomly getting file names

@echo off
setlocal
set _i=0
for %%a in (*) do (
call :exec set /a _i+=1
call :exec echo %%_i%%: %%a
)
endlocal
goto :eof

:exec
%*
goto :eof

goto :eof

[ Last edited by 220110 on 2006-8-20 at 21:36 ]

Re: brother bagpipe
A lot of very good batch files! Your post is really nice!

Re: brother 220110

The function of this batch file is to number all the files in the current directory in order!

@echo off

setlocal

set _i=0

for %%a in (*) do (

  call :exec set /a _i+=1

  call :exec echo %%_i%%: %%a

  )

endlocal

goto :eof



:exec

%*

goto :eof



goto :eof

After removing part of the code, the execution result is the same; so the :exec label in the batch file above should be redundant! When calling the :exec label, no parameters are being passed



%* is %1 %2 %3 ... 



@echo off

setlocal

set _i=0

for %%a in (*) do (

  call  set /a _i+=1

  call echo %%_i%%: %%a

  )

endlocal

As long as someone reads it, I'm fully satisfied........... after all, it's a post in English, so not many people care about it

─────────────────　Moderator Record　─────────────────
Executed by: Will Sort
Action: modified title - 22699 - Let's discuss and study this batch file together
Penalty: deducted the 6 credits awarded for posting this topic, and deducted an additional 2 credits as a penalty for a title rule violation
─────────────────　Moderator Record　─────────────────

Re bagpipe:

It's necessary to remind you that the titles of several of your topics have been rather vague. In the past, no action was taken in view of the relatively high quality of the content, and I hope similar problems will not appear again.

Also, please note that for reposted articles you must indicate the original link so readers can check it. Generally there is no need to combine and repost two articles together; if there really is such a need, please add the necessary markers where the texts join.

[ Last edited by willsort on 2006-8-22 at 02:14 ]

Re 220110:

As brother doscc said, %* represents the entire command-line argument list starting from %1.

The function of the :exec section should be to execute the passed-in command-line argument list once again as a new independent command line.

The difference between call :exec commands ... and call commands is that the former calls a label section inside the batch file itself, while the latter directly calls internal or external commands.

As for that piece of code, since the functions it implements are not the same, their efficiency is not really comparable.

Re doscc:

>When calling the :exec label, no parameters are being passed

In fact, parameters are being passed, otherwise %* would do nothing at all.

The reason it still works without calling :exec is that call has the characteristic of reconstructing the command-line environment (including the variable environment). Although under xp's cmd, :exec really does seem superfluous, the author's writing environment was NT/2K, which may not have had some of xpcmd's features (for example, delayed variable expansion was not supported before NT4.0(2000)), so a double-call or call :exec calling structure was used.

Also, I added simple comments to the final code in the article command line parameter parsing, as follows:

::@echo off

:: Separate the first argument in the command-line arguments from the remaining arguments

:: file: detach.cmd

:: Example: detach "123 456" abc  xyz

::                

:: Example: detach 123 " 456 abc" xyz

::                



setlocal

set argList=%*

call :detachArg1 argList

echo 

goto done



:: if no quotes, this is much simpler:

:: Because FOR/F's lexical analysis does not escape quotation marks, spaces inside quotes cannot be hidden

::     FOR /f "tokens=1*" %%a IN ("%*") DO echo 

:: detachArg1 arglistName

:: (split first arg from given argList)

::  detachArg1  = firstArg(*arglistName)

::  *arglistName = argTail(*arglistName)



:detachArg1

  set _detachArg1=

  if %1.==. goto :eof

  call call :firstArg %%%1%%

  call set %%^^%0%%=%firstArg%

:: Store the value of firstArg in an environment variable named after the current subroutine label, detachArg

:: The environment variable name does not contain the colon in the label (after the colon is modified by %^ it is escaped to empty), and variables with colons in their names are hard to reference

:: As the author said, the above two lines and the :firstArg section can be simplified to a single line: set detachArg1=%1

  call call :argTail %%%1%%

  set %1=%argTail%

:: Store the remaining return value of the subroutine, %argTail%, in the environment variable argList having the same name as the subroutine command-line parameter

  goto :eof



:: Store the first passed-in argument in the environment variable firstArg, named after the current subroutine label

:firstArg

  call set %%^^%0%%=%1

  goto :eof



:: Return the command-line argument list without the first argument — the tail of the command line

:: return argument list, without first.

:argTail

  set argList=%*

  set arg1=%1

  if not defined arg1 goto :eof

  call :varlength arg1

:: Get the string length of the first argument

  call call :trimlist %%argList:~%varlength%%%

:: Cut out the following part of the whole command line according to the length, and save it into trimlist

  call set %%^^%0%%=%trimlist%

:: Save the value of %trimlist% into argTail

:: The above two lines and the :trimlist section can be simplified to a single line: call set argTail=%%argList:~%varlength%%%

  goto :eof



:: String slicing

:trimlist

  call set %%^^%0%%=%*

  goto :eof



:: Use brute force to get the string length of environment variable arg1 (the first argument)

:: get length of environment variable (via brute force)

:: %1 name of var to check

:varlength

   for /f "tokens=1* delims==" %%y in ('set %1^|findstr /b /i "%1=" ') do (

     set vl_val=%%z)

   set vl_vlen=0

   if not defined vl_val goto lenrpdone

   :: trap quoted string

   :: Environment variables whose string value contains quotation marks can no longer be enclosed in one pair of quotation marks, so they must be handled differently

   if "".==%vl_val:~0,1%%vl_val:~-1%. (

        set vl_vlen=2

        set vl_val=%vl_val:~1,-1%

   ) else (

        set vl_vlen=0

   )

   :chklenrpdone

     if "%vl_val%"=="" goto lenrpdone

     set vl_val=%vl_val:~1%

     set /a vl_vlen+=1

     goto chklenrpdone

   :lenrpdone

   call set %%^^%0%%=%vl_vlen%

   set vl_vlen=

   set vl_val=

   goto :EOF



:done

endlocal

[ Last edited by willsort on 2006-8-22 at 02:49 ]

I really have nothing to say now. I was just about to reach Silver Member, and now this again — have to wait a few more days, sigh