Windows batch file - splitting a string to set variables

I feel like I'm going around in circles with FOR loop options.

I'm trying to take a string (output of a command) and split it on commas, then use each value to SET, e.g.

String: USER=Andy,IP=1.2.3.4,HOSTNAME=foobar,PORT=1234

So I want to split on comma and then literally use that variable in SET. I don't know ahead of time how many many variables there will be.

I've tried things like:

FOR %%L IN (%MYSTRING%) DO ECHO %%L

but that splits on the equals sign too so I end up with

USER
Andy
IP
1.2.3.4

etc

I just want to be able to do the following so I can SET USER=Andy etc, something like:

FOR %%L IN (%MYSTRING%) DO SET %%L

What option or flags am I missing?

Solution

The default delimiters for elements in plain FOR command (no /F option) are spaces, tab, commas, semicolons and equal signs, and there is no way to modify that, so you may use FOR /F command to solve this problem this way:

@echo off 

set MYSTRING=USER=Andy,IP=1.2.3.4,HOSTNAME=foobar,PORT=1234

:nextVar
   for /F "tokens=1* delims=," %%a in ("%MYSTRING%") do (
      set %%a
      set MYSTRING=%%b
   )
if defined MYSTRING goto nextVar
echo USER=%USER%, IP=%IP%, HOSTNAME=%HOSTNAME%, PORT=%PORT%

Another way to solve this problem is first taking the variable name and then executing the assignment for each pair of values in a regular FOR command:

setlocal EnableDelayedExpansion

set MYSTRING=USER=Andy,IP=1.2.3.4,HOSTNAME=foobar,PORT=1234

set varName=
for %%a in (%MYSTRING%) do (
   if not defined varName (
      set varName=%%a
   ) else (
      set !varName!=%%a
      set varName=
   )
)
echo USER=%USER%, IP=%IP%, HOSTNAME=%HOSTNAME%, PORT=%PORT%

EDIT 2023/01/20: New method added

I know this is a very old question. However, I can't resist the temptation to post a new very interesting method to solve this old problem:

@echo off 

set MYSTRING=USER=Andy,IP=1.2.3.4,HOSTNAME=foobar,PORT=1234

set "%MYSTRING:,=" & set "%"

echo USER=%USER%, IP=%IP%, HOSTNAME=%HOSTNAME%, PORT=%PORT%

If you want to know where the magic is, remove the @echo off line, execute the program and carefully review the screen...