sd_event_add_signal, sd_event_source_get_signal, sd_event_signal_handler_t — Add a UNIX process signal event source to an event loop
typedef struct sd_event_source sd_event_source;
|const struct signalfd_siginfo *si,|
sd_event_add_signal() adds a new UNIX
process signal event source to an event loop. The event loop
object is specified in the
and the event source object is returned in the
source parameter. The
signal parameter specifies the numeric
signal to be handled (see signal(7)).
handler parameter must reference a
function to call when the signal is received or be
NULL. The handler function will be passed
userdata pointer, which may be chosen
freely by the caller. The handler also receives a pointer to a
signalfd_siginfo structure containing
information about the received signal. See signalfd(2)
for further information.
Only a single handler may be installed for a specific
signal. The signal will be unblocked by this call, and must be
blocked before this function is called in all threads (using
the handler is not specified (
NULL), a default handler which causes the
program to exit cleanly will be used.
By default, the event source is enabled permanently
SD_EVENT_ON), but this may be changed with
If the handler function returns a negative error code, it will be
disabled after the invocation, even if the
SD_EVENT_ON mode was requested before.
To destroy an event source object use
but note that the event source is only removed from the event loop
when all references to the event source are dropped. To make sure
an event source does not fire anymore, even if it is still referenced,
disable the event source using
If the second parameter of
NULL no reference to the event source object
is returned. In this case the event source is considered
"floating", and will be destroyed implicitly when the event loop
itself is destroyed.
the configured signal number of an event source created previously
sd_event_add_signal(). It takes the
event source object as the
On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style error code.
Returned errors may indicate the following problems:
Not enough memory to allocate an object.
An invalid argument has been passed.
A handler is already installed for this signal or the signal was not blocked previously.
The event loop is already terminated.
The event loop has been created in a different process.
The passed event source is not a signal event source.
These APIs are implemented as a shared
library, which can be compiled and linked to with the