Symbolic links

FullPath folder = FullPath.FromFileSystemInfo(Directory.CreateTempSubdirectory());
FullPath file = folder / "data.txt";
File.WriteAllText(file, "");
FullPath link1 = folder / "link1.txt"; // link1.txt -> data.txt
File.CreateSymbolicLink(link1, file);
FullPath link2 = folder / "link2.txt"; // link2.txt -> link1.txt
File.CreateSymbolicLink(link2, link1);

Assert.True(link2.IsSymbolicLink());
Assert.False(file.IsSymbolicLink());

// The target stored in the link, which can be another link
Assert.True(link2.TryGetSymbolicLinkTarget(out FullPath? target));
Assert.Equal(link1, target);

// Follow the links until the target is not a link
Assert.True(link2.TryGetSymbolicLinkTarget(SymbolicLinkResolutionMode.FinalTarget, out FullPath? finalTarget));
Assert.Equal(file, finalTarget);

// The canonical path also resolves the links in the parent folders
Assert.True(link2.TryGetCanonicalPath(out FullPath? canonicalLink));
Assert.True(file.TryGetCanonicalPath(out FullPath? canonicalFile));
Assert.Equal(canonicalFile, canonicalLink);

Detect a link and read its target

• IsSymbolicLink tells whether the path is a symbolic link. It is false for the empty path.
• TryGetSymbolicLinkTarget returns the target of the link, as a FullPath. A relative target is resolved against the folder of the link. The method returns false when the path is not a symbolic link.

The SymbolicLinkResolutionMode parameter chooses how far to follow the links:

FinalTarget and AllSymbolicLinks throw an IOException after 40 links, which usually means that the links form a cycle.

The canonical path

TryGetCanonicalPath returns the final path of an existing file or folder: the operating system resolves the symbolic links and the reparse points of every segment. It returns false when the path does not exist or cannot be resolved.

A link and its target have the same canonical path. Compare canonical paths when links matter, for instance to check that a path stays inside a folder even through a link. The temporary folder itself can be under a link, as on macOS, where /var is a link to /private/var: the canonical path of a file can differ from the path you created it with.