How to properly set a variable from PowerShell in Windows batch file?

Question

For someone unknown reasons, I am unable to retrieve this variable on Windows batch file.

PowerShell:

$datePattern = [Regex]::new(\'value=(\\S+)\')
$         


        

Answer 1

Provided the file tmpfile IS a single line file and doesn't exceed max cmd line length.

Batch

:: Q:\Test\2018\12\30\SO_53977221_.cmd
@Echo off
set /P "string="

---

>  SO_53977221_.cmd
newvalue=12.2

This uses string substitution (with a wildcard) and substring to get the desried value.

A combined batch/powershell solution is also possible but requires a bit more effort with escaping and quoting than your try.

This PowerShell one liner will output

PoSh> if((Get-Content .\tmpfile) -match 'value=(\d\d\.\d)'){$Matches[1]}
12.2

Properly wrapped in batch

:: Q:\Test\2018\12\30\SO_53977221.cmd
@Echo off
for /f "usebackq" %%A in (`
    powershell -NoP -C "if((Get-Content .\tmpfile) -match 'value=(\d\d\.\d)'){$Matches[1]}"
`) Do set "newvalue=%%A"
set newvalue

Sample output:

> .\SO_53977221.cmd
newvalue=12.2