When a batch file modifies an environment variable, cmd.exe retains this change even after the script exits. This often causes problems, as one batch file can accidentally pollute the environment of another. That said, batch file authors sometimes intentionally change the global environment to customize the path and other aspects of the environment to suit a specific task.
However, environment variables are private details of a process and disappear when that process exits. This makes the environment customization scripts mentioned above stop working when you run them from PowerShell—just as they fail to work when you run them from another cmd.exe (for example, cmd.exe /c MyScript.cmd).
retain their changes even after cmd.exe exits. It accomplishes this by storing the environment variables in a text file once the batch file completes, and then setting all those environment variables again in your PowerShell session.
To run this script, type InvokeCmdScript Scriptname.cmd or InvokeCmdScript Scriptname.bat—whichever extension the batch files uses.
If this is the first time you’ve run a script in PowerShell, you will need to configure your Execution Policy.
Notice that this script uses the full names for cmdlets: GetContent, ForeachObject, SetContent, and RemoveItem. This makes the script readable and is ideal for scripts that somebody else will read. It is by no means required, though. For quick scripts and interactive use, shorter aliases (such as gc, %, sc, and ri) can make you more productive.
Example 16. InvokeCmdScript.ps1
############################################################################## ## ## InvokeCmdScript.ps1 ## ## Invoke the specified batch file (and parameters), but also propagate any ## environment variable changes back to the PowerShell environment that ## called it. ## ## i.e., for an already existing 'foothatsetstheFOOenvvariable.cmd': ## ## PS > type foothatsetstheFOOenvvariable.cmd ## @set FOO=%* ## echo FOO set to %FOO%. ## ## PS > $env:FOO ## ## PS > InvokeCmdScript "foothatsetstheFOOenvvariable.cmd" Test ## ## C:\Temp>echo FOO set to Test. ## FOO set to Test. ## ## PS > $env:FOO ## Test ## ##############################################################################
param([string] $script, [string] $parameters)
Example 16. InvokeCmdScript.ps1 (continued)
$tempFile = [IO.Path]::GetTempFileName( )
## Store the output of cmd.exe. We also ask cmd.exe to output ## the environment table after the batch file completes cmd /c " `"$script`" $parameters && set > `"$tempFile`" "
## Go through the environment variables in the temp file. ## For each of them, set the variable in our local environment. GetContent $tempFile | ForeachObject {
if($_ match "^(.*?)=(.*)$") { SetContent "env:\$($matches[1])" $matches[2] } }
RemoveItem $tempFile
