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PowerShell module filesystem: resolve-relativePath

The function resolve-relativePath of the module filesystem returns the relative path between a directory and a file or directory.

Thus, it improves the functionality provided by the built-in cmdlet resolve-path which only allows to get the relative path from the current directory ($pwd).

resolve-relativePath $fromDir  $destPath

Note: $fromDir and $destPath must share a common prefix in order for the function to succeed.

This function was inspired (and copied with minor adaptions) by/from Carbon's command Resolve-RelativePath.

The function uses the WinAPI function PathRelativePathTo.

It seems that the returned value of PathRelativePathTo always starts with a dot.

Simple example

$sql_file_root = 'P:\ath\to\development\sql'

foreach ($file in get-childItem $sql_file_root -recurse -include *.sql) {

    $rel_path = resolve-relativePath $sql_file_root $file
    $rel_path

}

Passing an array to the second parameter

The second parameter accepts an array:

PS:> resolve-relativePath  x/y  x/a/b, x/y/z, x/
..\a\b
.\z
..\

Quirk

The function currently calls PathRelativePathTo with the Directory attribute for the $fromDir and the Normal (File) attribute for $destPath.

Thus, when going from a directory to another, the function returns a somewhat quirky result (..\.. would already be ok):

PS: 32 C:/Users/igsnyre/a/b/c/d> resolve-relativePath   a/b/c/d   a/b
..\..\..\b

This behavior should probably be changed once.

PowerShell 7

In PowerShell 7 (Netstandard 2.1?), relative paths can apparently be queried like so:

[System.IO.DirectoryInfo]$x = './a/b/c/d'
[System.IO.DirectoryInfo]$y = './a/b/x/y'
[System.IO.Path]::GetRelativePath($x,$y)

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