SET Command Doesn't Echo FOR /F Loop Parameter Values [duplicate]

Question

I ran across an issue using the SET command inside a FOR /F loop to echo the values of the loop parameters (e.g., %%g, %%h, etc.). I used the SET command because I wanted to see what values get assigned to each FOR /F loop parameter when the FOR /F loop iterates. I am specifically looking to see how many caret escape characters (^) are stripped by the CMD parser as it processes the line of test code that is the last element in the $code_test[00] array record:

@echo off

setlocal disabledelayedexpansion

set $code_test[00]=Record [00],2,green,blue,if not exist ^^!$m^^!^^!$n^^! (set /a $result+=3)

echo Value using ECHO command:
echo $code_test[00] = %$code_test[00]%
echo.

echo Value using SET command with Delayed Expansion DISABLED:
set $code_test[
echo.

setlocal enabledelayedexpansion

echo Value using SET command with Delayed Expansion ENABLED:
set $code_test[
echo.

for /f "tokens=1-10 delims=," %%g in ('set $code_test[') do (

    echo For /f loop values using ECHO command ...
    echo g = %%g
    echo h = %%h
    echo i = %%i
    echo j = %%j
    echo k = %%k
    echo.

    echo For /f loop values using SET command ...
    set %%g
    set %%h
    set %%i
    set %%j
    set %%k

)

The code populates one record for the $code_test[xx] array with various elements, the last of which is a Windows CMD test code statement. I want to see the value of the FOR /F loop parameter that corresponds to this test code statement, which is %%k. So, I used both the echo and set commands to echo the value of %%k to see if %%k retained the caret (^) escape characters that were present in the original test code definition for $code_test[00]. The echo command worked as expected and stripped the caret escape characters (^) from the code. But the set command completely failed. I've read the post about how the CMD interpreter parses code here and I didn't see an answer to my question.

I realize that dealing with FOR /F loop parameters can be tricky. Should I just assume that I can't deal with FOR /F loop parameters directly (e.g., set %%k) and make it a policy to always assign the value of a FOR /F parameter to an environment variable then deal with the environment variable instead of the FOR /F parameter?

You have a fundamental error here. %%k is a for parameter. Suppose that %%k is "green". Then, echo %%k show the value of %%k, so it show "green". set varName command show the value of a variable. In this way, set %%k would show the value of a variable called "green", if such a variable exists... A for parameter (like %%k) is very different than an environment variable (like %k%). You always can manage a for parameter directly. If you prefer to asign it to a variable, then you need to use !delayedExpansion! in order to manage the variable. — Aacini
– Aacini, Commented Jul 12, 2019 at 16:50
Thanks, @Aacini, for the quick reply. Now I understand why the set command works the way it does with FOR parameters. This is REALLY helpful. If you wouldn't mind posting your reply as an answer I'll give you the credit. — Bill Vallance
– Bill Vallance, Commented Jul 12, 2019 at 17:44

Magoo · Accepted Answer · 2019-07-12 18:35:34Z

SET "blue62=108"
SET "%%%%k=hello"
ECHO after SET %%%%%%%% k errorlevel=!errorlevel!
set|FIND "k="

    echo For /f loop values using SET command ...
ECHO ++++++++++++++++!errorlevel!
    set %%g
    set %%h
    set %%i
    set %%j
ECHO :::::::::::::::::::::!errorlevel!
    SET if not exist !$m!!$n! (set /a $result+=3)
ECHO -----------!errorlevel!-------------------
ECHO :::::::::::::::::::::!errorlevel!
    SET "if not exist !$m!!$n! (set /a $result+=3)"
ECHO -----------!errorlevel!-------------------
    set %%k

)

I expanded your reporting to include the above code with these results:

For /f loop values using ECHO command ...
g = $code_test[00]=Record [00]
h = 2
i = green
j = blue
k = if not exist !$m!!$n! (set /a $result+=3)

after SET %%%% k errorlevel=0
For /f loop values using SET command ...
++++++++++++++++1
Environment variable 2 not defined
Environment variable green not defined
blue62=108
:::::::::::::::::::::1
-----------1-------------------
:::::::::::::::::::::1
-----------1------------------- Environment variable %k not defined

I believe this demonstrates that set simply acts strangely if confronted with an argument that is not a simple space-absent string with optional = for assignment.

What was really curious was that the Environment variable %k not defined did not appear with the original code.

I believe you're really expecting a 1970's vintage design to not only be bullet-proof but act in a consistent manner when supplied with unanticipated data. Just treat it like your grandma. Very capable, but easily confused.

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