sd_bus_slot_get_userdata(3) — Linux manual page



NAME         top

       sd_bus_slot_set_userdata, sd_bus_slot_get_userdata - Set and query
       the value in the "userdata" field

SYNOPSIS         top

       #include <systemd/sd-bus.h>

       void* sd_bus_slot_set_userdata(sd_bus_slot* slot, void* userdata);

       void* sd_bus_slot_get_userdata(sd_bus_slot* slot);

DESCRIPTION         top

       The userdata pointer allows data to be passed between the point where
       a callback is registered, for example when a filter is added using
       sd_bus_add_filter(3) or an asynchronous function call is made using
       sd_bus_call_async(3), and the point where the callback is called,
       without having any global state. The pointer has type void* and is
       not used by the sd-bus functions in any way, except to pass to the
       callback function.

       Usually, the userdata field is set when the slot object is initially
       registered.  sd_bus_slot_set_userdata() may be used to change it
       later for the bus slot object slot. Previous value of the field is
       returned. The argument and returned value may be NULL. It will be
       passed as the userdata argument to the callback function attached to
       the slot.

       sd_bus_slot_set_userdata() gets the value of the userdata field in
       the bus slot object slot.

RETURN VALUE         top

       On success, these functions return the value of the userdata field
       before the function call. If the slot object is NULL, NULL will be
       returned to signify an error, but this is not distinguishable from
       the userdata field value being NULL.

NOTES         top

       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

SEE ALSO         top

       systemd(1), sd-bus(3), sd_bus_slot_set_destroy_callback(3),
       sd_bus_add_match(3), sd_bus_slot_get_current_userdata(3)

COLOPHON         top

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systemd 246                                      SD_BUS_SLOT_SET_USERDATA(3)

Pages that refer to this page: 30-systemd-environment-d-generator(7)systemd.index(7)