How to store the result of a command expression in a variable using bat scripts?

Question

I have the command below to count all directories that that follow the pattern 20?????? :

\'dir /b \"20??????\" | find /c \"2\"\'

Answer 1

(dir /b "20??????" | find /c "2")>>x.txt  
set /p variable=

That's all.

Of course, if you don't want the file, just do this afterwards:

del x.txt

EDIT -- How to make the filename unique:

@Mai: use this to create a uniqe file name:

set timestamp=%date:.=%%time::=%
set timestamp=%timestamp:,=%
set timestamp=%timestamp:/=%
set timestamp=%timestamp:-=%
set filename=file%timestamp%.tmp

Add more replacements if the date format of your system culture has other characters inside