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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_BUS_S...USERDATA(3) sd_bus_slot_set_userdata SD_BUS_S...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 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
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 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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HTML rendering created 2024-06-26 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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