How to execute CMD commands in one line?

Question

cmd/bat

Script

set /a M=%NUMBER_OF_PROCESSORS%/2
echo %M% > 1.txt

It is executed, but if you try with one line:

set /a M=%NUMBER_OF_PROCESSORS%/2 & echo %M% > 1.txt

Writes in 1.txt "The mode of displaying commands on the screen (ECHO) is disabled."
How to make it work with one line?

Answer 1

Environment variables are fully supplied in a compound command before it is executed (to see this, you can leave the command output mode on):

set a=1
set a=2& echo %a%

or

set a=1
(
 set a=2
 echo %a%
)

- displays 1.
For delayed variable expansion, use
- in this case, before that, a command must be present in the batch file
or cmd.exemust be launched with a key /v, or the mode of delayed variable expansion by default must be set in the registry (see set /?, setlocal /?, cmd /?).
For delayed expansion of variables, even if the corresponding mode is not enabled, you can also use the command call:
By the way. In arithmetic assignment set /afor delayed expansion of variables, they can be written not as %var%or !var!, but simply var:
set /a M = NUMBER_OF_PROCESSORS / 2

Answer 2

SETLOCAL EnableDelayedExpansion & set /a M=%NUMBER_OF_PROCESSORS%/2 & echo !M!