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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_BUS_SL..._USERDATA(3) sd_bus_slot_set_userdataSD_BUS_SL..._USERDATA(3)
sd_bus_slot_set_userdata, sd_bus_slot_get_userdata - Set and query
the value in the "userdata" field
#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);
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.
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.
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.
sd_bus_slot_set_userdata() and sd_bus_slot_get_userdata() were
added in version 240.
systemd(1), sd-bus(3), sd_bus_slot_set_destroy_callback(3),
sd_bus_add_match(3), sd_bus_slot_get_current_userdata(3)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨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 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 258~rc2 SD_BUS_SL..._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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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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