The local filesystem, jailed under a root directory.

disk = Fil.disk(adapter: Fil.Adapter.Local, root: "priv/storage")

Behaviour

• writes are atomic: content goes to a temporary file in the destination directory and is then renamed into place, so readers never see a partial file. Missing parent directories are created first.
• if_exists: :error skips the temporary file and opens the destination with O_EXCL instead. If something is already there, the write returns a Fil.AlreadyExistsError.
• every path is checked against the root again after expansion. Fil has already rejected ../ escapes, so this is defense in depth. The check only looks at the path string: a symlink inside the root can still point outside it.
• listing a missing directory, or a path that isn't a directory, returns {:ok, []}, the same as a missing prefix on an object store.
• stat/3 sets :etag to a weak "size-mtime" tag. It's good enough to notice a change, but it can't prove there was none. :content_type is always nil, because the filesystem doesn't store one.
• the filesystem has no URLs. Attach Fil.Plugin.URL for public and signed URLs, and Fil.Plug serves them.
• the filesystem stores no checksums. checksum: on a write is accepted and ignored, and so is verify_checksum: true on a read. checksum: on a stat reads the whole file to compute it.

Options

• :root (String.t/0) - The directory every path is resolved against. Defaults to File.cwd!() when the disk is built, so changing the working directory later doesn't move the disk. A relative root is expanded once, when the disk is built.

Operations

Errors

:reason is the POSIX atom from File, adjusted so it's the same on macOS and Linux (deleting a directory is :eisdir on both, a parent that's a file :enotdir).