sd_event_run, sd_event_loop — Run an event loop
#include <systemd/sd-event.h>
int sd_event_run( | sd_event *event, |
uint64_t usec); |
int sd_event_loop( | sd_event *event); |
sd_event_run() may be used to run a single
iteration of the event loop specified in the
event parameter. The function waits until an event to
process is available, and dispatches the registered handler for
it. The usec parameter specifies the
maximum time (in microseconds) to wait for an event. Use
(uint64_t) -1 to specify an infinite
timeout.
sd_event_loop() invokes
sd_event_run() in a loop, thus implementing
the actual event loop. The call returns as soon as exiting was
requested using
sd_event_exit(3).
The event loop object event is
created with
sd_event_new(3).
Events sources to wait for and their handlers may be registered
with
sd_event_add_io(3),
sd_event_add_time(3),
sd_event_add_signal(3),
sd_event_add_child(3),
sd_event_add_defer(3),
sd_event_add_post(3)
and
sd_event_add_exit(3).
For low-level control of event loop execution, use
sd_event_prepare(3),
sd_event_wait(3)
and
sd_event_dispatch(3)
which are wrapped by sd_event_run(). Along
with
sd_event_get_fd(3),
these functions allow integration of an
sd-event(3)
event loop into foreign event loop implementations.
On failure, these functions return a negative errno-style
error code. sd_event_run() returns a
positive, non-zero integer if an event source was dispatched, and
zero when the specified timeout hit before an event source has
seen any event, and hence no event source was
dispatched. sd_event_loop() returns the exit
code specified when invoking
sd_event_exit().
Returned errors may indicate the following problems:
-EINVAL¶The event parameter is invalid or
NULL.
-EBUSY¶The event loop object is not in the right state (see sd_event_prepare(3) for an explanation of possible states).
-ESTALE¶The event loop is already terminated.
-ECHILD¶The event loop has been created in a different process, library or module instance.
Other errors are possible, too.
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.