sd_event_source_get_userdata(3) Set or retrieve user data pointer of event sources

Other Alias

sd_event_source_set_userdata

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

These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.

SEE ALSO

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