NAME

       sd_bus_attach_event, sd_bus_detach_event, sd_bus_get_event - Attach a bus connection
       object to an event loop

SYNOPSIS

       #include <systemd/sd-bus.h>

       int sd_bus_attach_event(sd_bus *bus, sd_event *e, int priority);

       int sd_bus_detach_event(sd_bus *bus);

       sd_event *sd_bus_get_event(sd_bus *bus);

DESCRIPTION

       sd_bus_attach_event() attaches the specified bus connection object to an sd-event(3) event
       loop object at the specified priority (see sd_event_source_set_priority(3) for details on
       event loop priorities). When a bus connection object is attached to an event loop incoming
       messages will be automatically read and processed, and outgoing messages written, whenever
       the event loop is run. When the event loop is about to terminate, the bus connection is
       automatically flushed and closed (see sd_bus_set_close_on_exit(3) for details on this). By
       default bus connection objects are not attached to any event loop. When a bus connection
       object is attached to one it is not necessary to invoke sd_bus_wait(3) or
       sd_bus_process(3) as this functionality is handled automatically by the event loop.

       sd_bus_detach_event() detaches a bus object from its event loop.

       The sd_bus_get_event() returns the event loop object the specified bus object is currently
       attached to, or NULL if it is currently not attached to any.

       Note that sd_bus_attach_event() is only one of three supported ways to implement I/O event
       handling for bus connections. Alternatively use sd_bus_get_fd(3) for hooking up a bus
       connection object with external or manual event loops. Or use sd_bus_wait(3) as a simple
       synchronous, blocking I/O waiting call.

RETURN VALUE

       On success, sd_bus_attach_event() and sd_bus_detach_event() return 0 or a positive
       integer. On failure, they return a negative errno-style error code.

       sd_bus_get_event() returns an event loop object or NULL.

   Errors
       Returned errors may indicate the following problems:

       -ECHILD
           The bus connection has been created in a different process, library or module
           instance.

NOTES

       Functions described here are available as a shared library, which can be compiled against
       and linked to with the libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be not multi-thread-safe.
       This means that the code calling the functions described here must not call setenv(3) from
       a parallel thread. It is recommended to only do calls to setenv() from an early phase of
       the program when no other threads have been started.

HISTORY

       sd_bus_attach_event(), sd_bus_detach_event(), and sd_bus_get_event() were added in version
       240.

SEE ALSO

       systemd(1), sd-bus(3), sd-event(3), sd_event_source_set_priority(3),
       sd_bus_set_close_on_exit(3), sd_bus_wait(3), sd_bus_get_fd(3)