Functions/Get-CommonPrefix.ps1
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function Get-CommonPrefix { <# .SYNOPSIS Find the common prefix of two strings. .DESCRIPTION This function will get the common prefix of two strings; that is, all the letters that they share, starting from the beginning of the strings. .EXAMPLE Get-CommonPrefix 'Card' 'Cartoon' Will get the common prefix of both string. Should output 'car'. .LINK https://communary.wordpress.com/ https://github.com/gravejester/Communary.PASM .INPUTS System.String .OUTPUTS System.String .NOTES Author: Øyvind Kallstad Date: 03.11.2014 Version 1.1 Dependencies: none #> [CmdletBinding()] param( [Parameter(Mandatory = $true, Position = 0)] [ValidateNotNullOrEmpty()] [string]$String1, [Parameter(Mandatory = $true, Position = 1)] [ValidateNotNullOrEmpty()] [string]$String2, # Maximum length of the returned prefix. [Parameter()] [int]$MaxPrefixLength, # Makes matches case-sensitive. By default, matches are not case-sensitive. [Parameter()] [switch] $CaseSensitive ) if (-not($CaseSensitive)) { $String1 = $String1.ToLowerInvariant() $String2 = $String2.ToLowerInvariant() } $outputString = New-Object 'System.Text.StringBuilder' $shortestStringLength = [Math]::Min($String1.Length,$String2.Length) # Let the maximum prefix length be the same as the length of the shortest of # the two input strings, unless defined by the MaxPrefixLength parameter. if (($shortestStringLength -lt $MaxPrefixLength) -or ($MaxPrefixLength -eq 0)) { $MaxPrefixLength = $shortestStringLength } # Loop from the start and add any characters found that are equal for ($i = 0; $i -lt $MaxPrefixLength; $i++) { if ($String1[$i] -ceq $String2[$i]) { [void]$outputString.Append($String1[$i]) } else { break } } Write-Output $outputString.ToString() } |