Why can't I redirect all output to a variable?

Question

So my understanding of powershell redirection is that *>&1 should redirect everything to the output stream.

Try the following from the visual studio package manager terminal on any project with Entity Framework migrations applied.

$m = (Get-Migrations *>&1)

After running, all your migrations are printed to the window, but $m is still $null.

What gives? Am I doing redirection wrong?

Edit: Seems like maybe I'm not and this should work. Here is the code for Get-Migrations

@Paul it prints out a list of the 20 or so migrations I have applied. Nothing gets stored in $m. I've seen this behavior before when using commandline tools which just write directly to the output stream rather than returning powershell objects. I seem to remember that in those cases I used redirection to resolve the issue but its not working here. — George Mauer
– George Mauer, Commented Dec 24, 2014 at 19:17
Hmm i see the cmdlet supports common parameters so you could try -outvariable — Paul
– Paul, Commented Dec 24, 2014 at 19:21
Suppose you could try to use Trace-Command if you really feel up to it. I cant since i dont have access to that type of environment. blogs.technet.com/b/heyscriptingguy/archive/2014/12/04/… — Matt
– Matt, Commented Dec 24, 2014 at 19:55

David Woods · Accepted Answer · 2014-12-24 22:08:58Z

2

[console]::WriteLine, which is what Get-Migrations is using, is basically the same as Write-Host, so it only prints the output and doesn't send anything through the pipeline like Write-Output does.

I found a dev named Lincoln Atkinson that has implemented a solution that uses a proxy for Write-Host at http://latkin.org/blog/2012/04/25/how-to-capture-or-redirect-write-host-output-in-powershell/

I've tested out his function and it seems to need a little work, it only worked for me when I passed the -Quiet flag. It also only works for Write-Host so updating it to work with WriteLine would be your take-home assignment from this....

Also it looks like while Start-Transcript might help (along with a generous parsing of output) if it were Write-Host based, but does not appear to catch [console]::WriteLine for whatever reason.

answered Dec 24, 2014 at 22:08

David Woods

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