How to call a function when Get-Content reads a line - powershell

Question

I am setting up a script that will send me an email every time a certain log file is written to but when Get-Content reads a new line, the pipe does not call the sendmail function.
The sendmail function is defined before the following line and successfully sends me an email by itself.
Get-Content -Tail 0 -Wait app.log | sendmail

Answer 1

You need to learn what a process block is. It runs for every element piped in. Put your code in the process block, and it will do what you want, as someone else already answered. Process blocks are really important in powershell.
function hi {
process {
'hi'
}
}
Get-Content -Tail 0 -Wait app.log | hi
hi
hi
hi

Answer 2

You should get the value from the pipeline through a process block:
function sendmail {
process {
$secpasswd = ConvertTo-SecureString "password" -AsPlainText -Force
$cred = New-Object System.Management.Automation.PSCredential ("username", $secpasswd)
Send-MailMessage -SmtpServer mysmtp -Credential $cred -UseSsl -From 'myemail#domain.com' -To 'toemail#domain.com' -Subject 'TEST'
}
}
This will tell PowerShell that you want this section of code to run for every object passed on the pipeline (every line in this case). If you want to access the current object from inside the process block, use $_ as a variable.
See Piping Objects to Functions