Best practice for emailing a body of appended strings? - powershell

Question

I have a Powershell script that automates a process and emails the report of what happened.
Send-MailMessage -To $toAddress -From "no-reply#domain.org" -subject "Automation status" -body $bodystr -SmtpServer SERVER1 -EA Stop
So $bodystr is essentially an appended string throughout the script to report what happened and has multiple lines. Things like:
$bodystr = $bodystr + "Line found: 305`n"
$bodystr = $bodystr + "Moving line 305 to 574`n"
The Send-MailMessage command is at the bottom of the script outside any function. But most other code is in various different functions.
The issue is $bodystr does not seem accessible inside functions, and so the email is lacking a lot of information.
I believe I could use Set-Variable or passing arguments, but there are so many arguments it seems farther away from best practice to add a new argument for each function just to keep the string updated.
What's the best practice to handle this?

Answer 1

As a general rule, don't write data back to variables outside the scope of your function.
If you are compiling an email by gathering data from multiple sources, abstract it away in multiple functions that does one thing each and have them return a multiline string with the relevant output.
At the end of your script, collect the different message body parts and join them to a single string before sending.
In this example, we have a script that takes a path to a log file, defines a function to extract errors from a log file, and send an email with the errors in the body:
param(
[ValidateScript({Test-Path $_ -PathType Leaf })]
[string]$LogPath = 'C:\Path\To\File.log',
[string]$From = 'noreply#company.example',
[string]$To = #('ceo#company.example','finance#company.example'),
[string]$Subject = 'Super Important Weekly Report',
[string]$SmtpServer = $PSEmailServer,
[string]$Credential
)
# Define functions with a straight forward purpose
# e.g. Searching a logfile for errors
function Parse-Logfile {
param($LogPath)
[string[]]$LogErrors = #()
Get-Content $LogPath |ForEach-Object{
if($_ -contains $Error){
$LogErrors += $_
}
}
# Create and return a custom object has the error details as properties
New-Object psobject -Property #{
ErrorCount = $LogErrors.Count
Errors = $LogErrors
}
}
# Create a email template that's easy to maintain
# You could store this in a file and add a $TemplateFile parameter to the script ;-)
$EmailTemplate = #'
Hi there!
Found {0} errors in log file: {1}
{2}
Regards
Zeno
'#
# Use your function(s) to create and gather the details you need
$ErrorReport = Parse-Logfile -LogPath $LogPath
# If necessary, concatenate strings with -join
$ErrorString = $ErrorReport.Errors -join "`n"
# Use the format operator to the final Body string
$Body = $EmailTemplate -f $ErrorReport.ErrorCount, $LogPath, $ErrorString
# Set up a splatting table (Get-Help about_Splatting)
$MailParams = #{
To = $To
From = $From
Subject = $Subject
Body = $Body
SmtpServer = $SmtpServer
}
if($PSBoundParameters.ContainsKey('Credential')){
$MailParams['Credential'] = $Credential
}
# Send mail
Send-MailMessage #MailParams