When working with Windows Command Prompt (cmd.exe), you might encounter issues when trying to store command output directly into environment variables. The naive approach using set var = command doesn't work as expected because:

REM This doesn't work as intended
set dow = powershell (get-date).dayofweek

The above actually creates a variable literally containing the command text rather than executing it and storing the output.

Here are three reliable methods to capture command output into environment variables:

Method 1: Using FOR /F with PowerShell

for /f "delims=" %%a in ('powershell (get-date).dayofweek') do set DOW=%%a
echo %DOW%

Method 2: Native CMD without PowerShell

for /f "tokens=1" %%a in ('wmic path win32_localtime get dayofweek /value ^| find "="') do set DOWNUM=%%a
set DOW=
if %DOWNUM% equ 0 set DOW=Sunday
if %DOWNUM% equ 1 set DOW=Monday
REM ...continue for all days
echo %DOW%

Method 3: Using Temporary Files

powershell (get-date).dayofweek > %temp%\dow.txt
set /p DOW=<%temp%\dow.txt
del %temp%\dow.txt
echo %DOW%

Here's how you might implement this in a backup batch file:

@echo off
:: Get current day of week
for /f "delims=" %%a in ('powershell (get-date).dayofweek') do set DOW=%%a

:: Create backup directory with day name
mkdir "C:\Backups\%DOW%"

:: Run your backup commands
xcopy "C:\ImportantData\*" "C:\Backups\%DOW%\" /s /e /h /k /y

echo Backup completed for %DOW%

For PowerShell 5.1+, you can use this more concise syntax:

for /f "delims=" %%a in ('powershell -command "[DateTime]::Now.DayOfWeek"') do set DOW=%%a

When working with Windows command-line automation, a common requirement is storing command output in environment variables for later use. The naive approach of set var = command doesn't work as expected because CMD processes the assignment literally rather than executing the command first.

The most reliable method in pure CMD uses the FOR /F construct to capture output:

@echo off
FOR /F "delims=" %%G IN ('powershell -command "(get-date).DayOfWeek"') DO SET DOW=%%G
echo Current day: %DOW%

Key points about this solution:

• The "delims=" prevents splitting the output at spaces
• Works with both standard CMD commands and PowerShell calls
• Variables persist for the current CMD session

If you're already in a PowerShell context, the approach is simpler:

$dow = (Get-Date).DayOfWeek
[Environment]::SetEnvironmentVariable("DOW", $dow, "User")

Here's how this technique applies to your backup scenario:

@echo off
:: Capture day of week
FOR /F "delims=" %%G IN ('powershell -command "(get-date).DayOfWeek"') DO SET DOW=%%G

:: Create backup directory with timestamp
FOR /F "delims=" %%H IN ('powershell -command "Get-Date -Format 'yyyyMMdd_HHmm'"') DO SET TIMESTAMP=%%H

mkdir "C:\Backups\%DOW%_%TIMESTAMP%"
xcopy "C:\Data\*.*" "C:\Backups\%DOW%_%TIMESTAMP%\" /E /H /C /I

• Always test with echo %VAR% after assignment
• For multi-line output, add usebackq option to FOR command
• Trim whitespace with SET VAR=%VAR: =% if needed

To make variables persist beyond the current session:

:: Temporary (session-only)
SET DOW=Friday

:: Permanent (requires admin)
SETX DOW "Friday"