Powershell select-string returns different values depending on number of matches

Try this:

$content = Get-Content $outputfilePath($content -match $regex).Count

Powershell has a number of Comparison Operators that will probably make your life easier. Here's a quick listing:

-eq-ne-gt-ge   -lt-le-Like-NotLike-Match-NotMatch-Contains-NotContains-In-NotIn-Replace

In this instance, -Match will match the $content string against your regular expression $regex, and the output is grouped by parenthesis. This grouping is a collection of strings. We can then Count the objects and print out an accurate count of matches.

So why doesn't your code work as expected? When you have a single match, .Matches actually returns a System.Text.RegularExpressions.Match object that looks something like this for a string "test123":

Groups   : {test123}Success  : TrueCaptures : {test123}Index    : 15Length   : 7Value    : test123

Why does this happen? Because a Microsoft.PowerShell.Commands.MatchInfo object is what Select-String returns. You can verify this by attempting some other properties like .Filename on your single-match output.

Okay, but why can't we get all of our matches in one go? This is because multiple matches will return multiple objects, so now you have a collection that you're trying to operate on. The collection has a different type, and doesn't understand .Matches. No collection is returned on 1 match, but instead a single object that does understand .Matches is!

Long story short: these aren't the outputs you're looking for!

You can use the array sub-expression operator @(...) to always place results in a collection with a Count:

(Select-String ...)        # may return $null, one match, or a collection of matches(Select-String ...).Count  # only succeeds for two or more matches@(Select-String ...)       # always returns a collection of matches@(Select-String ...).Count # always succeeds