Single line nested loop - windows

Question

I am experimenting with a single line cmd /c to get an inner loop without branching. (Actually i have the showLines routine which performs the loop.) I know its worst for performance but i want to know if its possible to get it run without quotes. Currently it raises "%G was unexpected at this time" error. So, it needs some correct escaping or expansion of variables.
#echo off
setlocal enableDelayedExpansion
set "param=%~1"
netstat -aonb | findstr /n $ > tmpFile_Content
for /F "tokens=*" %%A in ('type tmpFile_Content ^| findstr /r /c:"%param%" /i') do (
SET line=%%A
for /F "tokens=1 delims=:" %%I in ("!line!") DO (
set /a LineNum=%%I
rem set /a NextLineNum=LineNum+1
)
set /a lineNum=!LineNum!-1
if !lineNum!==0 ( set param="tokens=*" ) else ( set param="tokens=* skip=!lineNum!" )
rem FOLLOWING WORKS FINE in quotes
cmd /q /v:on /c "#echo off && setlocal enableDelayedExpansion && set cnt=2 && for /F %%param%% %%B in (tmpFile_Content) do ( echo %%B && set /a cnt-=1 >nul && if ^!cnt^!==0 exit /b )"
rem Following does not work even though cmd should take the rest of arguments after /c
cmd /q /v:on /c setlocal enableDelayedExpansion && FOR /F "tokens=*" %%C IN ('echo !param!') DO ( for /F %%C %%G in (tmpFile_Content) do ( echo %%G && set /a cnt-^=1 >nul && if ^!cnt^!==0 exit /b ))
rem call :showLines !LineNum!
)
del tmpFile_Content
goto :eof
:showLines
set /a lineNum=%1-1
set cnt=2
for /F "tokens=* skip=%lineNum%" %%B in (tmpFile_Content) do (
echo %%B
set /a cnt-=1
if !cnt!==0 goto exitLoop
)
:exitLoop
exit /b

Answer 1

to construct for loops with variable parameters, you essentially need to define and execute them as a macro. Eg:
#Echo Off & Setlocal ENABLEdelayedExpasnion
Set param="tokens=* delims="
Set "test=string line"
Set For=For /F %param% %%G in ("^!test^!") Do echo %%G
%For%
Of course you could go even further, and build the entire for loop with another for loop macro on the fly.
UPDATE:
Method for defining conditional concatenation of commands now exampled
Syntax simplified to allow the same usage form for regular expansion and within codeblocks by having the constructor macro call a subroutine to expand the new for loop once it's constructed.
delayed concatenation variable usage simplified to avoid the escaping requirement
#Echo off
::: { Macro Definition
Setlocal DisabledelayedExpansion
(set \n=^^^
%= This creates an escaped Line Feed - DO NOT ALTER =%
)
::: [ For Loop Constructor macro. ] For advanced programmers who need to use dynamic for loop options during code blocks.
::: - usage: %n.For%{For loop options}{variable set}{For Metavariable}{commands to execute}
::: - use delayed !and! variable to construct concatenated commands in the new for loop.
Set n.For=For %%n in (1 2) Do If %%n==2 (%\n%
Set FOR=%\n%
For /F "tokens=1,2,3,4 Delims={}" %%1 in ("!mac.in!") Do (%\n%
Set "FOR=For /F %%1 %%3 in ("!%%2!") Do (%%~4)"%\n%
)%\n%
Call :Exc.For%\n%
)Else Set mac.in=
Set "and.=&&"
Set "and=!and.!"
::: } End macro definition.
Setlocal EnableDelayedExpansion& rem // required to expand n.For constructor macro
::: - Usage examples:
Set "example=is a string line"
%n.For%{"tokens=* delims="}{example}{%%G}{Echo/%%~G}
%n.For%{"tokens=1,2,3,4 delims= "}{example}{%%G}{"Echo/%%~J %%~G %%~H %%~I !and! Echo/%%~I %%~G %%~H %%~J"}
Set "example2=Code block example"
For %%a in (1 2 3) do (
%n.For%{"Tokens=%%a Delims= "}{example2}{%%I}{"For /L %%# in (1 1 4) Do (Set %%I[%%#]=%%a%%#) !and! Set %%I[%%#]"}
)
Pause > Nul
Goto :EOF
:Exc.For
%FOR%
Exit /B
Example output:
is a string line
line is a string
string is a line
Code[1]=11
Code[2]=12
Code[3]=13
Code[4]=14
block[1]=21
block[2]=22
block[3]=23
block[4]=24
example[1]=31
example[2]=32
example[3]=33
example[4]=34

Answer 2

Finally, i came up with following to execute code given in string for anyone interested experimentally and may be for some insight about escaping and expansion.
I use macro instead of cmd which will be much more faster i think(not sure because its said that "call" also causes launch of cmd).
So, it is a simple one-liner without a lot of extra code. But things easily become complicated and when extra escaping and special characters used then #T3RR0R's macro routine would be a necessity.
#echo off
setlocal EnableDelayedExpansion
set "param=%~1"
netstat -aonb | findstr /n $ > tmpFile_Content
for /F "tokens=*" %%A in ('type tmpFile_Content ^| findstr /r /c:"%param%" /i') do (
SET line=%%A
for /F "tokens=1 delims=:" %%I in ("!line!") DO (
set /a LineNum=%%I
rem set /a NextLineNum=LineNum+1
)
set /a lineNum=!LineNum!-1
rem CORRECT QUOTING
if !lineNum!==0 ( set "param="tokens=*"" ) else ( set "param="tokens=* skip=!lineNum!"" )
rem FOLLOWING WORKS FINE in quotes
rem cmd /q /v:on /c "set cnt=2 && for /F ^!param^! %%B in (tmpFile_Content) do ( echo %%B && set /a cnt-=1 >nul && if ^!cnt^!==0 exit /b )"
rem For reading !cnt! use !x!cnt!x!.
rem Only one extra variable used, and in routine its replaced with !(exclamation) for our "cnt" variable.
set "x=^!x^!"
call :ExecCode "set cnt=2 && for /F ^!param^! %%%%B in (tmpFile_Content) do (echo %%%%B && set /a cnt=!x!cnt!x!-1 >nul && if !x!cnt!x!==0 (exit /b) )"
rem call :showLines !LineNum!
)
del tmpFile_Content
goto :eof
:ExecCode
setlocal
rem Replace with exclamation for variable
set "x=^!"
set "s=%~1"
%s%
endlocal
exit /b
:showLines
set /a lineNum=%1-1
set cnt=2
for /F "tokens=* skip=%lineNum%" %%B in (tmpFile_Content) do (
echo %%B
set /a cnt-=1
if !cnt!==0 goto exitLoop
)
:exitLoop
exit /b