Passing Powershell from Cmd with variable evaluation - powershell

Question

I want to use the following command
powershell -command "get-content %CONFIG_FILE% | %{$_ -replace \"APP_PATH=.+\",\"APP_PATH=%APP_DIR%\"}"
but with the evaluation of the %CONFIG_FILE% and the %APP_DIR% which are defined in the batch script using
set CONFIG_FILE=C:\B0_GW.cfg
set APP_DIR=C:\dbg\kernel
when i do so, i currently get the following issue:
The string is missing the terminator: ".
+ CategoryInfo : ParserError: (:) [], ParentContainsErrorRecordException
+ FullyQualifiedErrorId : TerminatorExpectedAtEndOfString
any ideas?

Answer 1

aschipfl has provided the crucial pointer in a comment on the question:
From within a batch file[1], you must escape % characters that you want to pass through to the target application as %%.
Otherwise, cmd interprets % as the start or end of an environment-variable reference (which in part happens by design in your command; e.g., %CONFIG_FILE%).
(You've already correctly escaped embedded " chars. in your command as \" for PowerShell).
Specifically, the % in the %{...} part of your command needs escaping (% is PowerShell's built-in alias for the ForEach-Object cmdlet):
powershell -command "get-content %CONFIG_FILE% | %% {$_ -replace \"APP_PATH=.+\",\"APP_PATH=%APP_DIR%\"}"
Alternatively, simply use the cmdlet's actual name, ForEach-Object, which obviates the need for escaping:
powershell -command "get-content %CONFIG_FILE% | ForEach-Object {$_ -replace \"APP_PATH=.+\",\"APP_PATH=%APP_DIR%\"}"
[1] Sadly, the behavior at cmd.exe's command prompt (in an interactive session) differs - see this answer.