Как захватить вывод ошибки только в переменной в PowerShell

Я хочу сохранить вывод stderr команды powershell в переменной. Я не хочу хранить его в файле, и я не хочу включать стандартный вывод, просто вывод ошибки.

Это перенаправляет stderr и stdout на переменную $output

Но я хочу сохранить только вывод ошибки в переменной (то же самое, что и содержимое файла error.txt выше), не записывая ничего в файл. Как это сделать?

Ответы

Ответ 1

Вы можете вызвать команду несколько иначе и использовать параметр -ErrorVariable в PowerShell

Invoke-Expression "$command $params" -ErrorVariable badoutput

$badoutput теперь будет содержать содержимое строки ошибки

Ответ 2

To add to arco444, specific exception can be obtained by using $badoutput[0].Exception.

https://blogs.msdn.microsoft.com/powershell/2006/11/02/erroraction-and-errorvariable/ has more information on to effectively use the ErrorAction and ErrorVariable parameters built into Powershell.

Here is the easiest way to show this working:


PS> Stop-Process 13,23
Stop-Process : Cannot find a process with the process identifier 13.
At line:1 char:13
+ Stop-Process  <<<< 13,23
Stop-Process : Cannot find a process with the process identifier 23.
At line:1 char:13
+ Stop-Process  <<<< 13,23

PS> Stop-Process 13,23 -ErrorAction Stop  # Only 1 error
Stop-Process : Command execution stopped because the shell variable "ErrorA
ctionPreference" is set to Stop: Cannot find a process with the process ide
ntifier 13.
At line:1 char:13
+ Stop-Process  <<<< 13,23 -ErrorAction Stop  # Only 1 error

PS> Stop-Process 13,23 -ErrorAction silentlycontinue  # No errors

PS> Stop-Process 13,23 -ErrorAction inquire  # ASK
Confirm
Cannot find a process with the process identifier 13.
[Y] Yes  [A] Yes to All  [H] Halt Command  [S] Suspend  [?] Help
(default is "Y"):h
Stop-Process : Command execution stopped because the user selected the Halt
 option.
At line:1 char:13
+ Stop-Process  <<<< 13,23 -ErrorAction inquire  # ASK
PS>
PS>
PS> Stop-Process 13,23 -ErrorVariable a -ErrorAction SilentlyContinue

PS> $a[0]
Stop-Process : Cannot find a process with the process identifier 13.
At line:1 char:13
+ Stop-Process  <<<< 13,23 -ErrorVariable a -ErrorAction SilentlyContinue

PS> $a[0] |fl * -Force

Exception             : Microsoft.PowerShell.Commands.ProcessCommandExcepti
                        on: Cannot find a process with the process identifi
                        er 13.
TargetObject          : 13
CategoryInfo          : ObjectNotFound: (13:Int32) [Stop-Process], ProcessC
                        ommandException
FullyQualifiedErrorId : NoProcessFoundForGivenId,Microsoft.PowerShell.Comma
                        nds.StopProcessCommand
ErrorDetails          :
InvocationInfo        : System.Management.Automation.InvocationInfo

PS> $a |ft TargetObject -force -auto
TargetObject
————
          13
          23




Now one thing that is not obvious to people is that you can specify a "+" in front of the variable name for ErrorVariable and we will ADD the errors to that variable.


PS> [email protected]()
PS> stop-process 13 -ea silentlycontinue -ErrorVariable err
PS> $err.count
1

PS> stop-process 23 -ea silentlycontinue -ErrorVariable +err
PS> $err.count
2
PS> $err
Stop-Process : Cannot find a process with the process identifier 13.
At line:1 char:13
+ stop-process  <<<< 13 -ea silentlycontinue -ErrorVariable err
Stop-Process : Cannot find a process with the process identifier 23.
At line:1 char:13
+ stop-process  <<<< 23 -ea silentlycontinue -ErrorVariable +err

Lastly,  you don’t need to type out –ErrorAction or –ErrorVariable, we have defined parameter aliases for these so you can just type –EA and -EV