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sd_event_source_set_userdata(3) — Linux manual page

SD_EVENT...USERDATA(3) sd_event_source_set_userdataSD_EVENT...USERDATA(3)

NAME        top

       sd_event_source_set_userdata, sd_event_source_get_userdata - Set       or retrieve user data pointer of event sources

SYNOPSIS        top

#include <systemd/sd-event.h>void* sd_event_source_set_userdata(sd_event_source *source,void *userdata);void* sd_event_source_get_userdata(sd_event_source *source);

DESCRIPTION        top

sd_event_source_set_userdata()may be used to set an arbitrary       user data pointer for the event source object specified assource.       The user data pointer is usually specified when creating an event       source object with calls such assd_event_add_io(3) orsd_event_add_time(3), and may be updated with this call. The user       data pointer is also passed to all handler callback functions       associated with the event source. Theuserdata parameter specifies       the new user data pointer to set, the function returns the       previous user data pointer. Note thatNULLis a valid user data       pointer.sd_event_source_get_userdata()may be used to query the current       user data pointer assigned to the event source objectsource.

RETURN VALUE        top

       On success,sd_event_source_set_userdata()andsd_event_source_get_userdata()return the previously set user data       pointer. On failure, they returnNULL.

NOTES        top

       Functions described here are available as a shared library, which       can be compiled against and linked to with thelibsystemd pkg-config(1) file.       The code described here usesgetenv(3), which is declared to be       not multi-thread-safe. This means that the code calling the       functions described here must not callsetenv(3) from a parallel       thread. It is recommended to only do calls tosetenv()from an       early phase of the program when no other threads have been       started.

HISTORY        top

sd_event_source_set_userdata()andsd_event_source_get_userdata()       were added in version 229.

SEE ALSO        top

sd-event(3),sd_event_add_io(3),sd_event_add_time(3),sd_event_add_signal(3),sd_event_add_child(3),sd_event_add_inotify(3),sd_event_add_defer(3),sd_event_source_set_description(3)

COLOPHON        top

       This page is part of thesystemd (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 isnot part of the original manual page), send a mail to       man-pages@man7.orgsystemd 258~rc2SD_EVENT...USERDATA(3)

Pages that refer to this page:sd-event(3), sd_event_add_child(3), sd_event_add_defer(3), sd_event_add_inotify(3), sd_event_add_io(3), sd_event_add_memory_pressure(3), sd_event_add_signal(3), sd_event_add_time(3), sd_event_source_get_event(3), sd_event_source_set_description(3), sd_event_source_set_destroy_callback(3), sd_event_source_set_prepare(3), systemd.directives(7), systemd.index(7)

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