1SD_EVENT_ADD_SIGNAL(3) sd_event_add_signal SD_EVENT_ADD_SIGNAL(3)
2
6 sd_event_add_signal, sd_event_source_get_signal,
7 sd_event_signal_handler_t - Add a UNIX process signal event source to
8 an event loop
9
11 #include <systemd/sd-event.h>
12 typedef struct sd_event_source sd_event_source;
14 typedef int (*sd_event_signal_handler_t)(sd_event_source *s,
16 const struct signalfd_siginfo *si,
17 void *userdata);
18 int sd_event_add_signal(sd_event *event, sd_event_source **source,
20 int signal, sd_event_signal_handler_t handler,
21 void *userdata);
22 int sd_event_source_get_signal(sd_event_source *source);
24
26 sd_event_add_signal() adds a new UNIX process signal event source to an
27 event loop. The event loop object is specified in the event parameter,
28 and the event source object is returned in the source parameter. The
29 signal parameter specifies the numeric signal to be handled (see
30 signal(7)). The handler parameter must reference a function to call
31 when the signal is received or be NULL. The handler function will be
32 passed the userdata pointer, which may be chosen freely by the caller.
33 The handler also receives a pointer to a signalfd_siginfo structure
34 containing information about the received signal. See signalfd(2) for
35 further information.
36 Only a single handler may be installed for a specific signal. The
38 signal must be blocked in all threads before this function is called
39 (using sigprocmask(2) or pthread_sigmask(3)).
40 By default, the event source is enabled permanently (SD_EVENT_ON), but
42 this may be changed with sd_event_source_set_enabled(3). If the handler
43 function returns a negative error code, it will be disabled after the
44 invocation, even if the SD_EVENT_ON mode was requested before.
45 To destroy an event source object use sd_event_source_unref(3), but
47 note that the event source is only removed from the event loop when all
48 references to the event source are dropped. To make sure an event
49 source does not fire anymore, even if it is still referenced, disable
50 the event source using sd_event_source_set_enabled(3) with
51 SD_EVENT_OFF.
52 If the second parameter of sd_event_add_signal() is NULL no reference
54 to the event source object is returned. In this case the event source
55 is considered "floating", and will be destroyed implicitly when the
56 event loop itself is destroyed.
57 If the handler parameter to sd_event_add_signal() is NULL, and the
59 event source fires, this will be considered a request to exit the event
60 loop. In this case, the userdata parameter, cast to an integer, is
61 passed as the exit code parameter to sd_event_exit(3).
62 sd_event_source_get_signal() returns the configured signal number of an
64 event source created previously with sd_event_add_signal(). It takes
65 the event source object as the source parameter.
66
68 On success, these functions return 0 or a positive integer. On failure,
69 they return a negative errno-style error code.
70 Errors
72 Returned errors may indicate the following problems:
73 -ENOMEM
75 Not enough memory to allocate an object.
76 -EINVAL
78 An invalid argument has been passed.
79 -EBUSY
81 A handler is already installed for this signal or the signal was
82 not blocked previously.
83 -ESTALE
85 The event loop is already terminated.
86 -ECHILD
88 The event loop has been created in a different process.
89 -EDOM
91 The passed event source is not a signal event source.
92
94 These APIs are implemented as a shared library, which can be compiled
95 and linked to with the libsystemd pkg-config(1) file.
96
98 systemd(1), sd-event(3), sd_event_new(3), sd_event_now(3),
99 sd_event_add_io(3), sd_event_add_time(3), sd_event_add_child(3),
100 sd_event_add_inotify(3), sd_event_add_defer(3),
101 sd_event_source_set_enabled(3), sd_event_source_set_description(3),
102 sd_event_source_set_userdata(3), sd_event_source_set_floating(3),
103 signal(7), signalfd(2), sigprocmask(2), pthread_sigmask(3)
104systemd 250 SD_EVENT_ADD_SIGNAL(3)