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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | NOTES | SEE ALSO | COLOPHON |
SD_EVENT_GET_FD(3) sd_event_get_fd SD_EVENT_GET_FD(3)
sd_event_get_fd - Obtain a file descriptor to poll for event loop
events
#include <systemd/sd-event.h>
int sd_event_get_fd(sd_event *event);
sd_event_get_fd() returns the file descriptor that an event loop
object returned by the sd_event_new(3) function uses to wait for
events. This file descriptor may itself be polled for POLLIN/EPOLLIN
events. This makes it possible to embed an sd-event(3) event loop
into another, possibly foreign, event loop.
The returned file descriptor refers to an epoll(7) object. It is
recommended not to alter it by invoking epoll_ctl(2) on it, in order
to avoid interference with the event loop's inner logic and
assumptions.
On success, sd_event_get_fd() returns a non-negative file descriptor.
On failure, it returns a negative errno-style error code.
Returned errors may indicate the following problems:
-EINVAL
event is not a valid pointer to an sd_event structure.
-ECHILD
The event loop has been created in a different process.
Example 1. Integration in the GLib event loop
/***
Copyright 2014 Tom Gundersen
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation files
(the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Software,
and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
***/
#include <stdlib.h>
typedef struct SDEventSource {
GSource source;
GPollFD pollfd;
sd_event *event;
} SDEventSource;
static gboolean event_prepare(GSource *source, gint *timeout_) {
return sd_event_prepare(((SDEventSource *)source)->event) > 0;
}
static gboolean event_check(GSource *source) {
return sd_event_wait(((SDEventSource *)source)->event, 0) > 0;
}
static gboolean event_dispatch(GSource *source, GSourceFunc callback, gpointer user_data) {
return sd_event_dispatch(((SDEventSource *)source)->event) > 0;
}
static void event_finalize(GSource *source) {
sd_event_unref(((SDEventSource *)source)->event);
}
static GSourceFuncs event_funcs = {
.prepare = event_prepare,
.check = event_check,
.dispatch = event_dispatch,
.finalize = event_finalize,
};
GSource *g_sd_event_create_source(sd_event *event) {
SDEventSource *source;
source = (SDEventSource *)g_source_new(&event_funcs, sizeof(SDEventSource));
source->event = sd_event_ref(event);
source->pollfd.fd = sd_event_get_fd(event);
source->pollfd.events = G_IO_IN | G_IO_HUP | G_IO_ERR;
g_source_add_poll((GSource *)source, &source->pollfd);
return (GSource *)source;
}
These APIs are implemented as a shared library, which can be compiled
and linked to with the libsystemd pkg-config(1) file.
sd-event(3), sd_event_new(3), sd_event_wait(3), epoll_ctl(3),
epoll(7)
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 2017-07-05. If you dis‐
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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 234 SD_EVENT_GET_FD(3)
Pages that refer to this page: sd-event(3), sd_event_run(3), sd_event_wait(3), systemd.directives(7), systemd.index(7)