Question

This is my code so far:

FOR /f %%G IN (temp.file) DO (
    echo %%G > temp
    first_char.exe temp > letter
    set /p myLetter =<letter
    echo %myLetter%
)

first_char.exe prints to the stdout the first char from the input file.

It prints:

ECHO is off.
ECHO is off.
ECHO is off.
ECHO is off.
ECHO is off.
ECHO is off.

(because I have 6 lines of text in temp.file).

Answer 1

I can’t see why you need a first_char exe file to extract a single char, a simple var:~0,1 should also work.

Your ECHO is off. problem is a problem of the expansion time of %myLetter%.
It’s expanded when the complete parenthesis block is parsed, at this time myLetter% is empty, therefor you got only empty lines.

setlocal EnableDelayedExpansion
FOR /f %%G IN (temp.file) DO (
    set "var=%%G"
    set "myLetter=!var:~0,1!"
    echo !myLetter!
)