sd_bus_slot_set_userdata(3) — Linux manual page

SD_BUS_S...USERDATA(3)  sd_bus_slot_set_userdata  SD_BUS_S...USERDATA(3)

NAME

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

SYNOPSIS

       #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

       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

       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

       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_slot_set_userdata() and sd_bus_slot_get_userdata() were
       added in version 240.

SEE ALSO

       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

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       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have
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       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-13.)  If you discover any rendering
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       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

systemd 257~devel                                 SD_BUS_S...USERDATA(3)

Pages that refer to this page: sd-bus(3), sd_bus_slot_set_description(3), sd_bus_slot_set_destroy_callback(3), systemd.directives(7), systemd.index(7)

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