command line - dos batch iterate through a delimited string

Question

I have a delimited list of IPs I'd like to process individually. The list length is unknown ahead of time. How do I split and process each item in the list?

@echo off
set servers=127.0.0.1,192.168.0.1,10.100.0.1

FOR /f "tokens=* delims=," %%a IN ("%servers%") DO call :sub %%a

:sub
    echo In subroutine

    echo %1
exit /b

Outputs:

In subroutine
127.0.0.1
In subroutine
ECHO is off.

Update: Using Franci's answer as reference, here's the solution:

@echo off
set servers=127.0.0.1,192.168.0.1,10.100.0.1

call :parse "%servers%"
goto :end


:parse
setlocal
set list=%1
set list=%list:"=%
FOR /f "tokens=1* delims=," %%a IN ("%list%") DO (
  if not "%%a" == "" call :sub %%a
  if not "%%b" == "" call :parse "%%b"
)
endlocal
exit /b

:sub
setlocal
echo In subroutine
echo %1
endlocal
exit /b

:end

Outputs:

In subroutine
127.0.0.1
In subroutine
192.168.0.1
In subroutine
10.100.0.1

Answer 1

The for command handles a number of delimiters by default. In this case you can do

@echo off

set servers=127.0.0.1,192.168.0.1,10.100.0.1

for %%i in (%servers%) do (
  echo %%i
)

If you run into a delimiter that is not natively supported, you could do a replace to first prepare the string so it is in the right format

@echo off

set servers=127.0.0.1@192.168.0.1@10.100.0.1
set servers=%servers:@=,%

for %%i in (%servers%) do (
  echo %%i
)

Using recursive calls has the chance to run out of stack space once you go over a certain number of items in the list. Also testing it, the recursion pattern seems to run a bit slower.