Batch file to change directory run from within powershell does nothing

Question

I have a small "dev.bat" batch file on my PATH which I run to switch to my development project directory in W:\. This works fine from CMD but not when run from PowerShell (or PWSH).

I have no other problems running .bat files from PowerShell.

PS C:\> type C:\dev.bat
W:
CD W:\dev
PS C:\> dev.bat

me@computer C:\
> W:

me@computer W:\dev
> CD W:\dev

PS C:\> echo "Why did dev.bat not change directory??"
Why did dev.bat not change directory??

PS C:\> W:
PS W:\>

No, cmd /c dev.bat makes no difference.

Answer 1

When run from PowerShell, batch files invariably run in a (cmd.exe) child process^[1], given that PowerShell itself doesn't understand the batch language.

Changing the working directory in a child process is limited to that child process (and its own children), and has no effect on the calling process; a child process cannot change the calling process' working directory.

Your only option is to:

• have your batch file echo (print) the desired working directory
• capture that path in PowerShell and pass it to Set-Location

If you don't want to change your batch file, use the following workaround:

Set-Location -LiteralPath (cmd /c 'dev.bat >NUL && cd')

# Or if you want to use the 'cd' alias for Set-Location and 
# are confident that path never has "[" characters in it (so that
# it can't be mistaken for a wildcard expression):
cd (cmd /c 'dev.bat >NUL && cd')

---

If batch files needn't be involved at all, and you just want a convenient way to create custom functions that change to a predefined location (working directory), place the following function in your $PROFILE file:

# Helper function to place in $PROFILE, which generates custom quick-cd
# functions, based on a function name and target directory path.
function New-QuickCD ($Name, $LiteralPath) {
  $funcDef = @"
function global:$Name { Push-Location -LiteralPath "$LiteralPath" } # quick-CD function
"@
  Invoke-Expression $funcDef # define in current session too
  $funcDef >> $PROFILE # append to $PROFILE
}

Note:

• The generated functions use Push-Location rather than Set-Location to enable easy returning to the previous location with Pop-Location (popd).

• For convenience, generated functions are also defined in the current session via Invoke-Expression^[2] on creation, so you don't have to reload (dot-source) $PROFILE or open a new session before you can call the newly generated function.

• Blindly appending to $PROFILE with >> means that if you redefine a function, the new definition will take effect, but the obsolete previous one will linger in the file, requiring manual cleanup; the comment # quick-CD function placed after each generated function is meant to facilitate that - see the bottom section for a more sophisticated version of New-QuickCD that updates old definitions in place.

• You can make the function more robust and convenient in a variety of ways: making the parameters mandatory, verifying the path's existence (by default), resolving the path to an absolute one - again, see the bottom section.

E.g., to create a function named dev that switches to W:\dev, you'd then call:

# Generate function 'dev', which switches to 'W:\dev', 
# append it to your $PROFILE file, and also define it in this session:
New-QuickCD dev W:\dev 

# Call it:
dev  # changes the current location to W:\dev; use 'popd' to return.

---

More robust, flexible New-QuickCD function:

It improves on the above version as follows:

• It makes the parameters mandatory.
• It verifies the existence of the target directory path.
• It defines the functions with support for a -PrintOnly switch that merely prints the function's target directory, without changing to it.
• It resolves a relative path to an absolute one first, so that you can run New-QuickCD foo . to define a function that switches to the absolute path of the current location.
• When you redefine a function, the previous definition is automatically updated:
  • In order to enable this functionality $PROFILE is rewritten as a whole, using the > redirection operator.
  • To remove functions, you must still edit $PROFILE manually.
• It comes with comment-based help; run help New-QuickCD -Examples, for instance.

function New-QuickCD {
  <#
  .SYNOPSIS
    Creates a custom quick-CD function.

  .DESCRIPTION
    Creates a custom quick-CD function and appends it your $PROFILE file.

    Such a function changes to a fixed location (directory) stored inside the 
    function, specified at creation time to allow for quickly changing to
    frequently used directories using a short name.

    For convenience, a newly created function is also defined for the running
    session (not just for all future sessions).

    The quick-CD functions use Push-Location to change location, which
    enables you to easily return to the previously active location with
    Pop-Location (popd).

    To determine what location a given quick-CD function *would* change to,
    invoke it with the -PrintOnly switch.

  .PARAMETER FunctionName
  The name of the quick-CD function to define.

  .PARAMETER DirectoryPath
  The literal path of the directory the quick-CD function should change to.
  If given a relative path, it is resolved to an absolute one first.
  For convenience, you may specify a *file* path, in which case that file's
  parent path is used.

  .NOTES
    Your $PROFILE file is recreated every time you use this function, using the
    > redirection operator, so as to support updating functions in place.

    To *remove* a quick-CD function, edit $PROFILE manually.

  .EXAMPLE
    New-QuickCD dev W:\dev

    Adds a 'dev' function to $PROFILE, which on invocation changes the current
    location to W:\dev
    * Call just 'dev' to change to W:\dev. Use popd to return to the previous
      location.
    * Call 'dev -PrintOnly' to print what location function 'dev' *would*
      change to.

  .EXAMPLE
    New-QuickCD proj .

    Adds a 'proj' function to $PROFILE, which on invocation changes to the 
    the location that is current at the time of calling New-QuickCd.

  #>
  param(
    [Parameter(Mandatory)] [string] $FunctionName,
    [Parameter(Mandatory)] [string] $DirectoryPath
  )

  Set-StrictMode -Version 1; $ErrorActionPreference = 'Stop'

  # Resolve the path to a full path. Fail if it doesn't exist.
  $fullPath = (Resolve-Path -ErrorAction Stop -LiteralPath $DirectoryPath).Path
  # As a courtesy, if the path is a *file*, we use its parent path instead.
  if (Test-Path -PathType Leaf $fullPath) {
    $fullPath = [IO.Path]::GetDirectoryName($fullPath)
  }

  # Define a comment that identifies the functions we add to $PROFILE as
  # quick-CD functions.
  $idComment = '<# quick-CD function generated with New-QuickCD #>'

  # Generate the new function's source code...
  #  * on a *single line*, which enables easy filtering when updating $PROFILE below
  #  * with a distinctive comment at the end of the line that identifies the
  #    function as a quick-CD function.
  #  * with the global: scope specifier, which makes it easier to call the
  #    same definition with Invok-Expression to make the function available in the
  #    current session too.
  $newFuncDef = @"
$idComment function global:$FunctionName { param([switch] `$PrintOnly) if (`$PrintOnly) { "$fullPath" } else { Push-Location -LiteralPath "$fullPath" } }
"@
  # ... define it in the current session (doing this *before* updating $PROFILE ensures early exit if the function name is invalid)
  Invoke-Expression $newFuncDef
  # ... and update $PROFILE:
  # Get the current content of $PROFILE
  [string] $currentProfileContent =  if (Test-Path -LiteralPath $PROFILE)  { Get-Content -Raw -LiteralPath $PROFILE }
  # Try to replace an existing definition.
  $newProfileContent = $currentProfileContent -replace ('(?m)^{0} function global:{1} .+$' -f [regex]::Escape($idComment), [regex]::Escape($FunctionName)), $newFuncDef
  if (-not $currentProfileContent -or $newProfileContent -ceq $currentProfileContent) { # Profile didn't exist or nothing was replaced -> we must append the new definition.
    $newProfileContent = $newProfileContent.TrimEnd() + [Environment]::NewLine * 2 + $newFuncDef
  }
  # Write the file.
  $newProfileContent > $PROFILE

}

---

^{[1] By contrast, batch files run in-process when invoked from cmd.exe, analogous to how PowerShell runs its *.ps1 scripts in-process. POSIX-like shells such as Bash, on the other hand, by default run their scripts in a child process, except when sourcing is used (., source)}

^{[2] While this is a safe use of Invoke-Expression, it should generally be avoided.}