How to get Variable in Variable (%var1%var2%%)

Question

I'm trying to get a String of an users input and then let the Text scroll.

What I have so far:

@echo off
setlocal
set /p myString=String:
cls

call :StringLenght result myString
:ECHO
set /a result=%result%-1
set myString=%mystring:~%result%%
echo %myString%
ping -n 2 localhost>nul
cls

:StringLenght <resultVar> <stringVar>
(   
    setlocal EnableDelayedExpansion
    set "s=!%~2!#"
    set "len=0"
    for %%P in (4096 2048 1024 512 256 128 64 32 16 8 4 2 1) do (
        if "!s:~%%P,1!" NEQ "" ( 
            set /a "len+=%%P"
            set "s=!s:~%%P!"
        )
    )
)
( 
    endlocal
    set "%~1=%len%"
    goto ECHO
)

Now at this Point it doesn't works:

set myString=%mystring:~%result%%

I can't get the String out of a variable when I'm in a variable %% (Sounds weird but I think you can imagine what I mean).

Answer 1

You need delayed expansion for this to work.

Here is the concept:

@echo off
setlocal EnableDelayedExpansion

set "mystring=mousetail"
set result=5
echo %mystring%
echo !mystring:~%result%!

Should be easy to implement into your code.

Answer 2

An alternative without delayed expansion is to use the call command like this:

@echo off

set "myString=something"
set "result=4"
echo %myString%
call echo %%myString:~%result%%%

What happens is that the expansion of Result is done immediately but the expansion of myString is carried out to the new cmd instance opened by call:

• firstly, the %% after echo is replaced by a single %;
• secondly, %result% is expanded, that is, replaced by its value 4;
• thirdly, the last %% is replaced by a single %;
• and lastly, the command line echo %myString:~4% is passed over to the new cmd instance opened by call, thus thing is displayed;

Notice, that this only works in a batch file but not in command prompt (cmd) directly.

---

In case you need delayed expansion for both nested variables, you could use a for loop:

@echo off

set "myString=something"
set "result=4"
setlocal EnableDelayedExpansion
echo !myString!
for %%I in (!Result!) do echo !myString:~%%I!
endlocal

This works because the for variable %%I is expanded before delayed expansion is applied, so the loop body receives the command line echo !myString:~4!.