Write-Warning

Write a warning message in reverse video to the host display.

Syntax
      Write-Warning [-message] string [CommonParameters]

Key
   -message string
       The warning message to send to the host.
       {may be piped}

   CommonParameters:
       -Verbose, -Debug, -ErrorAction, -ErrorVariable, -WarningAction, -WarningVariable,
       -OutBuffer -OutVariable.

Setting the $WarningPreference variable will alter the action of Write-Warning:

Continue Show the message on the console [this is the Default action]
SilentlyContinue do not show the message.
Stop show the message and then halt.
Inquire prompt the user.

Write-Warning (and Write-host) write only to the host/screen. To also have the output passed to the success pipeline, use Write-Output instead.

Example

Write a warning message:

PS C:\> $WarningPreference = "Continue"
PS C:\> Write-Warning "The quick brown fox."

“History is a vast early warning system” ~ Norman Cousins

Related:

Write-Debug - Write a debug message to the host display
Write-Error - Write an object to the error pipeline.
Write-Host - Display objects through the host user interface
Write-Output - Write an object to the pipeline
Write-Progress - Display a progress bar
Write-Verbose - Write a string to the host’s verbose display