More Preference Variables

I covered $ErrorActionPreference in the last post, but there are a few other preference variables that you might want to be aware of.  The full list can be found here.

$ConfirmPreference  (default value = 'High')

$ConfirmPreference sets the default level for the -Confirm option on cmdlets.  When a developer makes a cmdlet they have the option of setting the impact level to 'Low', 'Medium', or 'High'.  When a command is run, if the impact level is greater than or equal to the level in $ConfirmPreference, a confirmation prompt appears before the action is executed.  The confirmation prompt will look something like this:

Are you sure you want to perform this action?

Performing operation "Stop-Process" on Target "calc (5852)".

[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "Y"): 

To suppress confirmation prompts altogether, you can set $ConfirmPreference to $false, which is especially useful when scripting High impact operations.

$OFS (default value = ' ')

$OFS is the Output Record Separator.  Let's say I make an array and then print it, like so: 

PS C:\Users\tojo2000\Documents> $array = ('T', 'O', 'J', 'O')

PS C:\Users\tojo2000\Documents> echo $array

T

O

J

O

Each element of the array was echoed.  Notice what happens if we embed our array in a double-quoted string, though.

 

PS C:\Users\tojo2000\Documents> "My name is $array."

My name is T O J O.

Because the default value of $OFS is a single space, each element of the array is printed with a single space between.  We can set $OFS to be whatever we want, however:

PS C:\Users\tojo2000\Documents> $OFS = ' to the '

PS C:\Users\tojo2000\Documents> "My name is $array."

My name is T to the O to the J to the O.

$DebugPreference (default value = 'SilentlyContinue')

$ProgressPreference (default value = 'Continue')

$VerbosePreference (default value = 'SilentlyContinue')

$WarningPreference (default value = 'Continue')

These preference variables tell PowerShell what to do if it comes across a Debug, Progress (when using the Write-Progress cmdlet, for example), Verbose, or Warning message.  

The possible options are:

• Inquire - print the message, then prompt to continue
  
• Continue - print the message, then continue
  
• SilentlyContinue - suppress the message, then continue
  
• Stop - error out of the script or cmdlet