Write-Host

Write-Host has had a bad press over the years culminating in the infamous saying “if you use Write-Host a puppy will die” or words to that effect.

So what’s the fuss about?

Let’s take some code

Write-Host -Object “starting”

function t1 {
Write-Host -Object “In the function”

2+2

}

Write-Host -Object “pre-function”

t1

Write-Host -Object “post-function”

It’s not quite the world’s most fantastic piece of code but it’ll do for now

When you run this code you see output like this:

starting

pre-function

In the function

4

post-function

The problem is that you can’t easily separate the code output from the Write-Host messages as Write-Host does what it says and writes your message direct to the host.

What you should be doing is using one of the more specific Write cmdlets:

Write-Debug

Write-Error

Write-Host

Write-Information

Write-Progress

Write-Verbose

Write-Warning

Maybe in this case Write-Information

Write-Information -MessageData “starting”  -InformationAction Continue

function t1 {
Write-Information -MessageData “In the function” -InformationAction Continue
2+2

}

Write-Information -MessageData “pre-function” -InformationAction Continue

t1

Write-Information -MessageData “post-function” -InformationAction Continue

with output of

starting

pre-function

In the function

4

post-function

But this looks just like Write-Host.  In PowerShell v5 and later Write-Host is a wrapper for Write-Information

To see the difference remove the –InformationAction parameter and use this horribly contrived code

$inf = @()

Write-Information -MessageData “starting” -InformationVariable a

$inf += $a

function t1 {
Write-Information -MessageData “In the function” -InformationVariable a

$inf += $a

2+2

}

Write-Information -MessageData “pre-function” -InformationVariable a

$inf += $a

t1

Write-Information -MessageData “post-function” -InformationVariable a

$inf += $a

If you look at the contents of $inf you see the messages

starting

pre-function

post-function

Notice you’ve lost the message from within the function – we’ll come back to that another time

You have a record with some interesting data

PS> $inf | gm


    TypeName: System.Management.Automation.InformationRecord

Name            MemberType Definition                                         
----            ---------- ----------                                         
Equals          Method     bool Equals(System.Object obj)                     
GetHashCode     Method     int GetHashCode()                                  
GetType         Method     type GetType()                                     
ToString        Method     string ToString()                                  
Computer        Property   string Computer {get;set;}                         
ManagedThreadId Property   uint32 ManagedThreadId {get;set;}                  
MessageData     Property   System.Object MessageData {get;}                   
NativeThreadId  Property   uint32 NativeThreadId {get;set;}                   
ProcessId       Property   uint32 ProcessId {get;set;}                        
Source          Property   string Source {get;set;}                           
Tags            Property   System.Collections.Generic.List[string] Tags {get;}
TimeGenerated   Property   datetime TimeGenerated {get;set;}                  
User            Property   string User {get;set;}

For instance

PS> $inf | select TimeGenerated, MessageData

TimeGenerated       MessageData  
-------------       -----------  
29/06/2018 20:25:44 starting     
29/06/2018 20:25:44 pre-function 
29/06/2018 20:25:44 post-function

could be useful for tracing progress

There’s a lot more in the write cmdlets that we’ll come back to another time