Concatenating PowerShell variables - powershell

Question

$timeout = new-timespan -Minutes 1
$sw = [diagnostics.stopwatch]::StartNew()
$path = "d:\powershell\test.csv"
"Processor Load, Available Memory(MB), Max Memory(Bytes)" >> $path
while ($sw.elapsed -lt $timeout)
{
$a = gwmi -query "Select * from win32_processor"
$b = gwmi -query "Select * from win32_perfrawdata_perfOS_memory"
$c = gwmi -query "Select * from win32_physicalmemory"
$date = Get-Date -format s
$a.loadpercentage + "," + $b.availableMbytes + "," + $c.capacity >> $path
start-sleep -seconds 5
}
So I'm just looking to get a minute long snapshot of what's going on. I'm not just opening this in perfmon for reasons. Basically I'd expect to get a comma-delimited output in the CSV file mentioned. It works for a single variable, but when I try to add a second variable, or text I get the following error.
Cannot convert value ", test" to type "System.Int32". Error: "Input string was not in a
correct format."
At D:\powershell\VDIPerfMon.ps1:14 char:21
+ $a.loadpercentage + <<<< ", test" >> $path
+ CategoryInfo : NotSpecified: (:) [], RuntimeException
+ FullyQualifiedErrorId : RuntimeException
How can I fix this problem?

Answer 1

When you use the + operator PowerShell looks on the left hand side to determine the resulting type of the expression. It is seeing an int on the left of the + and a string (that can't be converted to an int) on the right. Try it this way:
"$($a.loadpercentage), $($b.availableMbytes), $($c.capacity)" >> $path
Also where you write your headers, you might not want to append i.e. in order to overwrite old attempts:
"Processor Load, Available Memory(MB), Max Memory(Bytes)" > $path

Answer 2

The error is because $a.loadpercentage is an int. You are then trying to add an int and a string.
One workaround is to explicitly call .ToString()
$a.loadpercentage.ToString() + "," + $b.availableMbytes.ToString() + "," + $c.capacity.ToString() >> $path
Another way is the PowerShell array join operator. It is quick easy, and types do not matter:
($a.loadpercentage, $b.availableMbytes, $c.capacity) -join "," |
Add-Content $path
Yet another way is with a string formatter. This will easily let you control the precision and display of each value:
'{0},{1},{2}' -f $a.loadpercentage, $b.availableMbytes, $c.capacity