# sd_bus_attach_event

## 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.
    


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