Subshells in Powershell

Previously, I wrote a post about how it's possible to create a "subshell" in Windows analogous to the subshell feature available in Bash on Linux—because Microsoft Windows doesn't actually have native subshell capability the same way that Linux does. The script below is an improvement on the same previous method of using the .NET System.Diagnostics trick. But this new version correctly redirects the standard output:

$x = New-Object System.Diagnostics.ProcessStartInfo
$x.FileName = "cmd.exe"
$x.Arguments = "/c echo %PATH%"
$x.UseShellExecute = $false
$x.RedirectStandardOutput = $true  
$x.EnvironmentVariables.Remove("Path")
$x.EnvironmentVariables.Add("PATH", "C:\custom\path")
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $x
$p.Start() | Out-Null
$output = $p.StandardOutput.ReadToEnd()
$p.WaitForExit()
Write-Output $output

Real-World Example

$customPath2 = "C:\custom\path\2"

$data = @{
    Path = $customPath2  
    Timestamp = Get-Date
    ProcessID = $PID  
}

$x = New-Object System.Diagnostics.ProcessStartInfo
$x.FileName = "cmd.exe"
$x.Arguments = "/c echo %PATH%"
$x.UseShellExecute = $false
$x.RedirectStandardOutput = $true
$x.RedirectStandardError = $true

$data["SubshellError"] = $stderr

$x.EnvironmentVariables.Remove("Path")
$x.EnvironmentVariables.Add("PATH", $customPath2)

$p = New-Object System.Diagnostics.Process
$p.StartInfo = $x
$p.Start() | Out-Null

$output = $p.StandardOutput.ReadToEnd()
$stderr = $p.StandardError.ReadToEnd() 
$p.WaitForExit()

$data["SubshellOutput"] = $output
$data["SubshellError"] = $stderr

$data

> $data

Name                           Value
----                           -----
ProcessID                      11852
Path                           C:\custom\path\2
SubshellOutput                 C:\custom\path\2...
SubshellError
Timestamp                      3/10/2025 7:05:01 PM