NAME

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

SYNOPSIS

       #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

       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

       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

       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_event_source_set_userdata() and sd_event_source_get_userdata() were added in version
       229.

SEE ALSO

       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)