在PowerShell中“ $？”是什么意思

Question

I'm very new to PowerShell. While looking up information about error handling I've found a lot of references to using "$?"

I know that it has something to do with errors but what exactly is it? And where can I read more about it?

All of my Google searches have found nothing.

Answer 1

From the The Essential Windows PowerShell Cheat Sheet :

Errors and Debugging: The success or failure status of the last command can be determined by checking $?

Example:

> Get-Content file-that-exists.txt
Hello world
> Write-Host $?
True
> Get-Content file-that-does-not-exist.txt
Get-Content : Cannot find path 'C:\file-that-does-not-exist.txt' because it does not exist.
At line:1 char:1
+ Get-Content file-that-does-not-exist.txt
+ ~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (C:\file-that-does-not-exist.txt:String) [Get-Content], ItemNotFoundException
    + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetContentCommand
> Write-Host $?
False

Answer 2

Just after asking this I discovered the command "Get-Help -name about_automatic_variables"

This gives information about every automatic variable in powershell, it's very helpful