# filesystem::read

> Tag 4: the client names one file of the container; the server sends its bytes as responses and the finish, or an error and the finish.

Canonical: https://protocol.diverge.network/2.3.0/container-proxy-endpoints/filesystem-read/
Specification revision: 2.3.0

The client opens the scope with a request whose payload is the tag
byte `4` followed by the path of one file, as JSON. The server sends
the bytes of the file as zero or more responses, or an error, and
ends the scope by the response finish. Neither party opens a channel
on a read scope.

- **The request.** [Request](/2.3.0/container-proxy-endpoints/filesystem-read/request/) states its form.
- **The response.** [Response](/2.3.0/container-proxy-endpoints/filesystem-read/response/) states the sequence of
  the main stream.

## The order

1. **The server reads the request.** A request whose payload does not
   decode is answered by a response finish that no response precedes,
   as [Container Proxy Endpoints](/2.3.0/container-proxy-endpoints/) provides. A path that is
   the root, or that has a component that is empty, `.`, `..`, or
   contains `/` or NUL, is answered by exactly one error response and
   the finish.
2. **The server opens the file.** As the operating system opens it, a
   symbolic link followed. A file that cannot be opened, and a path
   that is not a regular file once opened, are answered by exactly
   one error response and the finish.
3. **The server sends the bytes.** As responses, each at most
   `CHUNK_SIZE` bytes, in order, until the file is read. A file of
   zero bytes is sent as exactly one response of zero bytes. A read
   that fails is answered by exactly one error response after the
   responses already sent.
4. **The server finishes the scope.**