Shorten a path in PowerShell Core 7+

shorten-path.ps1

# Shorten a path in PowerShell by omitting segments from the beginning.
# Parameter defaults are designed to be used in a prompt.
# Requires at least PowerShell Core 7.

function shorten-path {
  <#
  .SYNOPSIS
  Shortens a path from the end.

  .DESCRIPTION
  Shortens a path by omitting segments from the beginning. Useful e.g. to shorten the CWD in prompt.

  .EXAMPLE
  PS> shorten-path 'C:\foo\bar\baz\qux'
  foo\bar\baz\qux

  .EXAMPLE
  PS> shorten-path -Path 'C:\foo\bar\baz\qux'
  foo\bar\baz\qux

  .EXAMPLE
  PS> 'C:\foo\bar\baz\qux' | shorten-path
  foo\bar\baz\qux

  .EXAMPLE
  PS> shorten-path -MaxLength 5 'C:\foo\bar\baz\qux'
  baz\qux

  .EXAMPLE
  PS> shorten-path -MaxLength 1 'C:\foo\bar\baz\qux'
  qux

  .EXAMPLE
  PS> shorten-path -MaxSegments 3 'C:\foo\bar\baz\qux'
  bar\baz\qux

  .EXAMPLE
  PS> shorten-path -MaxSegments 0 'C:\foo\bar\baz\qux'
  C:\foo\bar\baz\qux
  #>

  [CmdletBinding(PositionalBinding = $false)]
  param (
    [Parameter(ValueFromPipeline, Position = 0, HelpMessage = "The path to shorten.")]
    [string]
    $Path = (Get-Location),

    [Parameter(HelpMessage = "Maximum number of path segments to keep, 0 to disable. Defaults to 4.")]
    [int]
    $MaxSegments = 4,

    [Parameter(HelpMessage = "Maximum length of shortened path, 0 to disable. Defaults to 1/3 of the terminal width, minimum 30.")]
    [int]
    $MaxLength = [math]::Max(
      [math]::Round($Host.UI.RawUI.WindowSize.Width) / 3,
      30
    )
  )

  $array = @();

  # Fallback result is a single folder
  $result = $Path | Split-Path -Leaf;

  $max_i = ($MaxSegments -eq 0 ? [double]::PositiveInfinity : $MaxSegments);
  for ($i = 0; $i -lt $max_i; $i++) {
    # Get the path leaf for the current iteration
    # (e.g. iterated leaf for $i = 1 of "C:\foo\bar" would be "foo")
    $iterated_leaf = $Path;
    for ($j = 0; $j -lt $i; $j++) {
      $next_iterated_leaf = ($iterated_leaf | Split-Path);

      # Bail out if file system root was reached early
      if ($next_iterated_leaf.Length -eq 0) {
        Write-Verbose "Done; root segment '$iterated_leaf' was reached."
        return $result;
      }

      $iterated_leaf = $next_iterated_leaf;
    }
    $iterated_leaf = ($iterated_leaf | Split-Path -Leaf);

    $array = $array + $iterated_leaf;
    $reversed = $array[($array.Length - 1)..0];
    $next_result = (($reversed.Length -eq 1) ?
      $reversed[0] :
      (Join-Path @reversed));

    # Bail out if maximum path length was reached early
    if (($MaxLength -gt 0) -And ($next_result.Length -gt $MaxLength)) {
      if ($array.Length -eq 1) {
        Write-Verbose "Done; initial segment '$($iterated_leaf)' already exceeds maximum length ($MaxLength)."
      }
      else {
        Write-Verbose "Done; maximum length ($MaxLength) would be exceeded with additional segment '$($iterated_leaf)'."
      }
      return $result;
    }

    $result = $next_result;
  }

  Write-Verbose "Done; maximum number of segments ($MaxSegments) reached."
  return $result;
}