How to insert PowerShell variables into a string block

Question

Quick question, i'm trying to insert a variable into a string json body block like below, but when i perform a rest api call by passing the json body into the invoke-webrequest function, the variable is actually not getting inserted. In the alert software i'm using i just see the message as 'The following host $($scrapperHost) is not running!!'

 #variable
    $myHost = $Env:Computername
    #variable prints the correct hostname
    #string json body
    $jsonBody = @'
    {
        "message": "The following host $($myHost) is not running!!"}
    }

Santiago Squarzon · Accepted Answer · 2024-07-31 19:53:05Z

There are several ways you can insert variables into strings or Here-Strings. See about Quoting Rules for related information.

For your specific example, variables are expanded in double-quotes so instead of using @'...'@ you can use @"..."@:

$myHost = $env:COMPUTERNAME

$jsonBody = @"
{
    "message": "The following host $myHost is not running!!"
}
"@

Another way to do it is with format string or format operator -f, notice in this case, because the string contains { and } you must escape them with a consecutive curly brace:

$jsonBody = @'
{{
    "message": "The following host {0} is not running!!"
}}
'@ -f $myHost

Taking a step back, the correct way to do create your Json string would be to use ConvertTo-Json:

$jsonBody = [pscustomobject]@{
    message = "The following host $myHost is not running!!"
} | ConvertTo-Json

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