Loop through ASCII codes in batch file

Question

How do I loop through ASCII values (here, alphabets) and work on them?

I want to echo A to Z without having to type every character manually like for %%J in (A B C D E F G H I J K L M N O P Q R S T U V W X Y Z) do echo %%J

So I was wondering if I can cycle through ASCII codes. Something like for %%J in (ASCII of A ie.65 to Z) do echo %%J

Any help would be appreciated.

Answer 1

Surprisingly, there is a solution that makes use of an undocumented built-in environment variable named =ExitCodeAscii, which holds the ASCII character of the current exit code¹ (ErrorLevel):

@echo off
for /L %%A in (65,1,90) do (
    cmd /C exit %%A
    call echo %%^=ExitCodeAscii%%
)

The for /L loop walks through the (decimal) character codes of A to Z. cmd /C exit %%A sets the return code (ErrorLevel) to the currently iterated code, which is echo-ed as a character afterwards. call, together with the double-%-signs introduce a second parsing phase for the command line in order to get the current value of =ExitCodeAscii rather than the one present before the entire for /L loop is executed (this would happen with a simple command line like echo %=ExitCodeAscii%). Alternatively, delayed expansion could be used also.

The basic idea is credited to rojo and applied in this post: How do i get a random letter output in batch.

_{1) The exit code (or return code) is not necessarily the same thing as the ErrorLevel value. However, the command line cmd /C exit 1 sets both values to 1. To ensure that the exit code equals ErrorLevel, use something like cmd /C exit %ErrorLevel%.}