Can't print tail data from log file to PowerShell console once a variable is assigned

Question

I'm attempting to create a script that notifies me when a Windows application is down by monitoring a log file for specific keywords:

Get-Content <file> -Tail -Wait | Select-String -Pattern <keyword>

I also tried

Get-Content <file> -Tail -Wait | where {$_ -match <keyword>}

I can successfully retrieve the keyword that tells me the server is down using both variations of Get-Content shown above. I know it's successful because I see the line of the keyword displayed on console. However, when I attempt to assign a variable:

$var = Get-Content <file> -Tail -Wait | Select-String -Pattern <keyword>
Write-Host $var
$var

It no longer displays the line containing the string on the console

Here's the actual script:

$Downstate = Get-Content -Path "C:\Program Files (x86)\logs\log1.txt" -Tail 1 -Wait |
             Select-String -Pattern "tcp_disconnect"

Write-Host $Downstate

$Downstate

I also tried:

$Downstate = Get-Content -path "C:\Program Files (x86)\logs\log1.txt" -Tail 1 -Wait |
             where {$_ -match "tcp_disconnect"}

I tried both Write-Host and Write-Content BTW.

I get no errors when I assign to a variable, I just can't see the output on the console. But if I don't assign to a variable, I can see the output.

Ultimately what I want is to assign a variable to an up and down condition so that I can reference to them in my script when I'm ready to create a logic that does something during given condition.

Answer 1

The following approach works for me:

$infile = 'D:\PShell\DataFiles\so_57360147.txt'    ## my test case
$infile = 'C:\Program Files (x86)\logs\log1.txt'
Get-Content -path "$infile" -Tail 1 -Wait | 
    Select-String -pattern "tcp_disconnect" |
        ForEach-Object { 
            $Downstate = $_
            Write-Host $Downstate -Foreground Cyan ## debugging
            $Downstate                             ## real output
        }

Explanation derived from the Get-Content docs Parameters:

Wait

Keeps the file open after all existing lines have been output. While waiting, Get-Content checks the file once each second and outputs new lines if present. You can interrupt Wait by pressing CTRL+C. Waiting also ends if the file gets deleted, in which case a non-terminating error is reported.

Wait is a dynamic parameter that the FileSystem provider adds to the Get-Content cmdlet. This parameter works only in file system drives. Wait cannot be combined with Raw.