How can I prepend a timestamp to every PowerShell output line?

Question

I am trying to make PowerShell automatically prepend a timestamp to every line subsequent to invoking my custom ShowTimeStamps function. The function attempts to redirect output thru a filter that prepends the timestamp.

function ShowTimeStamps { $originalOutput = $host.UI.RawUI.WriteLine $host.UI.RawUI.WriteLine = { $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss.fffffff" Write-Host "$timestamp $_" } }

The above function is accepted by Powershell, but cannot be successfully invoked. It produces the error:

The property 'WriteLine' cannot be found on this object. Verify that the property exists and can be set. At line:3 char:5 + $host.UI.RawUI.WriteLine = { + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidOperation: (:) [], RuntimeException + FullyQualifiedErrorId : PropertyAssignmentException

seems like you're trying to override the builtin function prompt. assigning a value to WriteLine (a method) is not valid in this case — Santiago Squarzon
– Santiago Squarzon, Commented Oct 13, 2023 at 16:10

mklement0 · Accepted Answer · 2023-10-19 17:08:29Z

It sounds like you want to prefix every output line with a timestamp (Santiago's answer shows you how add a timestamp to the prompt line).

While overriding the Out-Default cmdlet in regular user code is normally to be avoided, here you can use a proxy function that combines Out-String -Stream with Out-Host to do what you want:

function Out-Default { [CmdletBinding()] param( [Parameter(ValueFromPipeline)] $InputObject ) begin { $scriptCmd = { Out-String -Stream | ForEach-Object { (Get-Date -Format 'yyyy-MM-dd HH:mm:ss.fffffff ') + $_ | Out-Host } } $steppablePipeline = $scriptCmd.GetSteppablePipeline($myInvocation.CommandOrigin) $steppablePipeline.Begin($PSCmdlet) } process { $steppablePipeline.Process($InputObject) } end { $steppablePipeline.End() } }

Once this function is defined (and in scope), every line in to-host output will be prefixed with a timestamp; e.g.:

 PS> Get-Date 2023-10-13 13:31:57.2870780 2023-10-13 13:31:57.2872810 Friday, October 13, 2023 1:31:57 PM 2023-10-13 13:31:57.2873870

Captured or redirected output will not be affected (however, on trying to display captured / redirected output, timestamps will again surface).
- However, the timestamps are captured in session transcripts created with Start-Transcript.
To revert to the default display behavior, simply remove the function:
```
 Remove-Item Function:Out-Default 
```
For more information about proxy functions, see this answer.

Santiago Squarzon · Accepted Answer · 2023-10-13 16:43:34Z

It's not clear what exactly you're looking for, it seems you may be looking to override your built-in prompt function. Overriding it to display the date in your desired format is quite easy, as an example:

function prompt { "PS $($ExecutionContext.SessionState.Path.CurrentLocation) - $([datetime]::Now.ToString('yyyy-MM-dd HH:mm:ss.fffffff'))$('>' * ($nestedPromptLevel + 1)) " }

Then your prompt would show the current location followed by a hyphen followed by the date and time in your desired format:

PS C:\Users\user - 2023-10-13 13:39:58.1856995>

This is of course as customizable as you want.

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