System.Systemd.Daemon.Fd

This module implements all functions from System.Systemd.Daemon that require or return Sockets purely using Fds. This is especially useful if you have to do low level IO using file descriptors or use a different socket library than network.

The API is exactly the same as System.Systemd.Daemon except that Sockets have been replaced by Fds (actually System.Systemd.Daemon uses this module internally). This also means that System.Systemd.Daemon.Fd and System.Systemd.Daemon expose conflicting functions. You either have to import System.Systemd.Daemon.Fd qualified or like so:

import System.Systemd.Daemon hiding ( notifyWithFD, storeFd
                                    , storeFdWithName
                                    , getActivatedSockets
                                    , getActivatedSocketsWithNames )
import System.Systemd.Daemon.Fd

The functions in System.Systemd.Daemon that are not implemented in this module are 100% compatible with System.Systemd.Daemon.Fd.

Notify functions

notifyWithFD :: Bool -> String -> Fd -> IO (Maybe ())

Same as notify, but send along a Fd. Note that the caller must set the message, i. e. send FDSTORE=1 to actually store the file descriptor. In most cases it is probably best to use storeFd or the notify-functions from System.Systemd.Daemon.

Equivalent to standard notifyWithFD.

storeFd :: Fd -> IO (Maybe ())

Notify Systemd to store a file descriptor for us. This together with getActivatedSockets allows for zero downtime restarts and socket activation.

Equivalent to standard storeFd

storeFdWithName :: Fd -> String -> IO (Maybe ())

Like storeFd, but associate the file descriptor with a name. Best used along with getActivatedSocketsWithNames.

Equivalent to standard storeFdWithName

Socket activation functions

getActivatedSockets :: IO (Maybe [Fd])

Return Just a list of file descriptors if the current process has been activated with one or more socket by systemd, Nothing otherwise.

The file descriptors are in the same order as the sockets in the associated .socket file. The sockets will have their family, type, and status set according to the .socket file.

Equivalent to standard getActivatedSockets

getActivatedSocketsWithNames :: IO (Maybe [(Fd, String)])

Like getActivatedSockets, but also return the associated names. If a file descriptor has no associated name, it will be a generic one set by systemd.

Equivalent to standard getActivatedSocketsWithNames