sd_event_source_set_userdata(3) — Linux manual page


SD_EVEN...SERDATA(3)  sd_event_source_set_userdata  SD_EVEN...SERDATA(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 as
       source. The user data pointer is usually specified when creating
       an event source object with calls such as sd_event_add_io(3) or
       sd_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. The userdata parameter
       specifies the new user data pointer to set, the function returns
       the previous user data pointer. Note that NULL is 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 object source.

RETURN VALUE         top

       On success, sd_event_source_set_userdata() and
       sd_event_source_get_userdata() return the previously set user
       data pointer. On failure, they return NULL.

NOTES         top

       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

HISTORY         top

       sd_event_source_set_userdata() and sd_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),

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ 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

systemd 257~devel                                   SD_EVEN...SERDATA(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)