It is always fun to write on a topic that people are passionate
about. Yes, we will be talking about Write-Host in this post. I know, you either love it or you hate it.
PowerShell uses different “streams” of information. Here is a quick visual.
Stream | Definition | Cmdlet
1 |
Success output |
Write-Output
2 |
Errors |
Write-Error
3 |
Warning messages |
Write-Warning
4 |
Verbose output |
Write-Verbose
5 |
Debug messages |
Write-Debug
6 |
Informational messages | Write-Information
NA |
User Experience |
Write-Host
The above is a little display that I use in class. Yes, it is created with Write-Host. Write-Host is OK to use if you need to
create a user interface of some type.
PowerShell was designed to use the pipeline. This is stream 1. Notice that there is no stream for Write-Host. Write-Host
sends information directly to the monitor.
There is a stream for Write-Information.
Write-Information
became available with PowerShell 5. Why
do we have another cmdlet to put information on the screen? Well, first of all,
the end user cannot stop Write-Host
from working. Take a look at this.
PS C:\>
$InformationPreference
SilentlyContinue
The information stream is controlled by a global variable
called $InformationPreference. Write-Host
has no such global variable controlling it.
By default, your information messages are not displayed.
PS C:\> Write-Information -MessageData "Nothing will
display"
PS C:\>
However, you can override this in code.
PS C:\> Write-Information -MessageData "Something
will display" -InformationAction Continue
Something will display
The –InformationAction
parameter is one of the common parameters.
That means the user running the code can ask for your information messages
if they want to see them. You can also redirect
the output of your information stream to another stream if it is
appropriate. You cannot do that with Write-Host because it sends information
directory to the screen. Below is a
comparison of the two commands.
|
Feature
|
Write-Host
|
Write-Information
|
|
Writes directly to the screen
|
Yes
|
No
|
|
Can display colors
|
Yes
|
No
|
|
Can be suppressed by the user
|
No
|
Yes
|
|
Can be redirected to another stream
|
No
|
Yes
|
|
Can have TAGs in the metadata
|
No
|
Yes
|
|
Can be saved in a variable
|
No
|
Yes
|
I understand the draw that Write-Host has with its ability
to display colors. If you are creating a
script that requires user interaction, go for it. If you want code that works well with the
pipeline and does not display information on the screen (Which can slow
processing times) then consider making the switch to Write-Information.
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