'for' statement in macro will not accept 'tokens' argument from another 'for' statement. Why?

[techtony]

Code: Select all

   set get_element=^
   for /l %%N in (1 1 2) do if %%N equ 2 (^
      for /f "tokens=1-3 delims= " %%A in ("^!args^!") do (^
         for /f "tokens=%%B delims=," %%X in (^!%%A^!) do (^
            set "%%C=%%X"^
         )^
      )^
   ) else set args=


   set lst="one,two,three"
   %get_element% lst 2 el
   echo,el: [%el%]

Output:

%B delims=," was unexpected at this time.
el: []

A function that does the same thing, however, does work:

Code: Select all

:GetElement
   for /f "tokens=%2 delims=," %%a in (!%1!) do (
      set %3=%%a
	)
exit /b

(Aside: Can the tab size in the code editor be changed? (I used 3 spaces in this post).)

[dbenham]

Because FOR /F options are parsed and interpreted before FOR variables are expanded.
The fact that you are using FOR /F within a macro has nothing to do with the problem.

It all makes sense if you study How does the Windows Command Interpreter (CMD.EXE) parse scripts?. You cannot use FOR variables or delayed expansion as options to IF or FOR because they are expanded too late. The IF and FOR variables are interpreted in phase 2. But FOR variables aren't expanded until phase 4, and delayed expansion is in phase 5.


Dave Benham

[techtony]

The macroization attempt, though, does introduce the problem. The macroization was, of course, done to avoid the overhead of a function call (which would have been a nice little snippet if it would have worked!). Thanks for your explanation.

[pieh-ejdsch]

a little workaround to do this ...

Code: Select all

set "varCount=!varName!"
set "varCount=!varCount:?=x"
set "varCount="=x!"
set "varCount="!varCount:,=" "!""
set "#=0"
for %%L in (!varCount!) do  ( set /a #+=1
  if !#! equ !TOKEN#!  for /f "delims=," %%S in ("!varName!") do set "newVar=%%S"
  set "varName=!varName:*,=!,")

[penpen]

Another option is to use string replacement within environment variables:

Code: Select all

@echo off
setlocal enableExtensions enableDelayedExpansion

set get_element=^
for /l %%N in (1 1 2) do if %%N equ 2 (^

^ for /f "tokens=1-3 delims= " %%A in ("^!args^!") do (^

^  for /f "tokens=_tokens delims=," %%X in (^^^!%%A^^^!) do (^

^   set "%%C=%%X"^

^  )^

^ )^

^) else set args=

set "get_element"

set lst="one,two,three"
%get_element:_tokens=2% lst 2 el
echo,el: [%el%]

Result:

Code: Select all

get_element=for /l %N in (1 1 2) do if %N equ 2 (
 for /f "tokens=1-3 delims= " %A in ("!args!") do (
  for /f "tokens=_tokens delims=," %X in (!%A!) do (
   set "%C=%X"
  )
 )
) else set args=
el: [two]

penpen

[techtony]

penpen wrote: "Another option is to use string replacement within environment variables."

That looked promising, but as the element number is likely to come from a variable and not a literal, that technique doesn't work. (That detail was not in the OP, because I was just pondering the situation, but it still seems like a good problem, but perhaps not solveable with batch).

[T3RRY]

Simpler would be:

Code: Select all

@Echo off
Setlocal DisableDelayedExpansion
 Set "Extract=Set "r=1"&For %%v in (!Tkns!)Do Set "#n=1"&For %%n in (1 2)Do if %%n==2 (For %%G in (!Var!)Do If "!#n!"=="%%v" (Set "!rv![!r!]=%%~G"&Set /A "#n+=1"& Set /A "r+=1")Else (Set /A "#n+=1"))Else Set Rv="
 Set "CLR=(For /F "tokens=1,2 Delims==" %%G in (' Set Var[ ') Do Set "%%~G=")2> Nul "
Setlocal EnableDelayedExpansion

 set "lst=one,two,three,four"
 Set Tkns=1 3 & %Extract:Var=lst%result
 Set result[
 %CLR:Var=result%
 Set result[ 2> Nul
ENDLOCAL & ENDLOCAL