Cannot run elixir application from powershell

Question

When I type iex -S mix in PowerShell I get this error:

Invoke-Expression : A positional parameter cannot be found that accepts argument 'mix'.
At line:1 char:1
+ iex S mix
+ ~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Invoke-Expression], ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,Microsoft.PowerShell.Commands.InvokeExpressionCommand

What is the correct way to write the '-S mix' after the 'iex' command to get the same effect typing it in cmd would do? This is an issue with me not understanding PowerShell syntax I believe.

Answer 1

The problem is that iex is an alias in Powershell, short for Invoke-Expression. If you're trying to run a command iex.exe, iex.bat or iex.cmd, you'll have to specify it in some unique way: an explicit (or full) path, or even just adding the application's extension may be enough. That way, Powershell won't try to run Invoke-Expression.

Get-Command can clear this sort of thing up for you:

PS C:\Dir> Get-Command iex

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Alias           iex -> Invoke-Expression 

PS C:\Dir> Get-Command cmd

CommandType     Name                                               ModuleName
-----------     ----                                               ----------
Application     cmd.exe

It doesn't seem to be possible to list both the command type and path at the same time: if you want to see which iex is which, you can use this form:

PS C:\Dir> Get-Command -All iex -Syntax
Invoke-Expression
C:\windows\iex.bat

You can find out more about how Powershell decides which command to run in Microsoft's technet library.

Answer 2

For anyone else who may see this question:

Short answer--to run iex from within Powershell type iex.bat. In this particular case iex.bat -S mix

Answer 3

If you use Elixir across different platforms and don't need yet another source of inconsistency (such as needing to remember use iex.bat instead of iex) you can remove the Invoke-Expression alias like so:

Remove-Item alias:\iex -Force

Now you can iex -S mix or whatever to your heart's content. Just be aware that this can conflict with other scripts you might run which assume iex is aliasing Invoke-Expression. For example I've had problems with the Azure SDK when un-binding iex, but I don't do Elixir and Azure dev on the same machine any more and I haven't run into any other issues yet.

If you want to have this happen automatically, add it to your Powershell profile. Easiest way is running notepad $PROFILE from Powershell and then add Remove-Item alias:\iex -Force near the end of your profile script.