Extract left part of HTTP URI containing scheme, host and port (everything before the path)

Question

PS C:\Users\user> Split-Path "http://localhost:9200/index" -Parent
http:\\localhost:9200

In above example, I am trying to extract everything before the /index. I thought Split-Path would do the job but it changes the forward slashes in http:// to back slashes.

"http://localhost:9200/index" -replace ([Uri]"http://localhost:9200/index").AbsolutePath

I've worked out the above alternative which works but Split-Path just seems cleaner. Just wondering why it does that with the forward slashes?

Answer 1

Split-Path works with provider paths only. Instead, use the .NET class Uri that is specifically made for parsing URIs.

Using the method Uri.GetLeftPart(), a partial URI can be extracted from the URI. This is much easier than building it "manually" by concatenating the URI components.

$uri = [uri] 'http://localhost:9200/index'
$uri.GetLeftPart('Authority')

# or as a one-liner:
([uri] 'http://localhost:9200/index').GetLeftPart('Authority')

Output:

http://localhost:9200

---

By passing other values from the UriPartial enum, different parts of the URI can be returned:

$uri = [uri] 'http://localhost:9200/index?param=value#anchor'

foreach( $part in 'Scheme','Authority','Path','Query' ) {
    [pscustomobject]@{
        Part = $part
        URI  = $uri.GetLeftPart( $part )
    }
}

Output:

Part      URI
----      ---
Scheme    http://
Authority http://localhost:9200
Path      http://localhost:9200/index
Query     http://localhost:9200/index?param=value

---

As noted by this related C# answer, there is one catch with Uri.GetLeftPart():

If the port is the default port for the scheme, it will strip it out. E. g., the URI http://localhost:80/index gets turned into http://localhost/index, because port 80 is the default for the HTTP scheme.

If this is a problem, then you may use the UriBuilder class to manually build the new URI from the parts of the original URI, while avoiding direct string manipulation:

Function Get-UriBase( [Parameter(Mandatory, ValueFromPipeline)] [Uri] $Uri ) {
    process {
        $uriBase = [UriBuilder]::new( $uri.Scheme, $uri.Host, $uri.Port ).ToString()
        # Output $uriBase if original URI starts with this part
        if( $uri.OriginalString.StartsWith( $uriBase ) ) { 
            return $uriBase 
        }
        # Otherwise original URI didn't contain a port, so use GetLeftPart() which omits it
        $uri.GetLeftPart('Authority')
    }
}

foreach( $uri in 'http://localhost:80/index', 'http://localhost:1234/index', 'http://localhost/index' ) {
    # For output in table format
    [PSCustomObject]@{ URI = $uri; URI_Base = Get-UriBase $uri }
}

Output:

URI                         URI_Base
---                         --------
http://localhost:80/index   http://localhost:80/  
http://localhost:1234/index http://localhost:1234/
http://localhost/index      http://localhost