1SD_EVENT_ADD_SIGNAL(3)        sd_event_add_signal       SD_EVENT_ADD_SIGNAL(3)
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3
4

NAME

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

SYNOPSIS

11       #include <systemd/sd-event.h>
12
13       typedef struct sd_event_source sd_event_source;
14
15       typedef int (*sd_event_signal_handler_t)(sd_event_source *s,
16                                                const struct signalfd_siginfo *si,
17                                                void *userdata);
18
19       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
23       int sd_event_source_get_signal(sd_event_source *source);
24

DESCRIPTION

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)).
31
32       The handler parameter is a function to call when the signal is received
33       or NULL. The handler function will be passed the userdata pointer,
34       which may be chosen freely by the caller. The handler also receives a
35       pointer to a signalfd_siginfo structure containing information about
36       the received signal. See signalfd(2) for further information. The
37       handler may return negative to signal an error (see below), other
38       return values are ignored. If handler is NULL, a default handler that
39       calls sd_event_exit(3) will be used.
40
41       Only a single handler may be installed for a specific signal. The
42       signal must be blocked in all threads before this function is called
43       (using sigprocmask(2) or pthread_sigmask(3)).
44
45       By default, the event source is enabled permanently (SD_EVENT_ON), but
46       this may be changed with sd_event_source_set_enabled(3). If the handler
47       function returns a negative error code, it will either be disabled
48       after the invocation, even if the SD_EVENT_ON mode was requested
49       before, or it will cause the loop to terminate, see
50       sd_event_source_set_exit_on_failure(3).
51
52       To destroy an event source object use sd_event_source_unref(3), but
53       note that the event source is only removed from the event loop when all
54       references to the event source are dropped. To make sure an event
55       source does not fire anymore, even if it is still referenced, disable
56       the event source using sd_event_source_set_enabled(3) with
57       SD_EVENT_OFF.
58
59       If the second parameter of sd_event_add_signal() is NULL no reference
60       to the event source object is returned. In this case the event source
61       is considered "floating", and will be destroyed implicitly when the
62       event loop itself is destroyed.
63
64       If the handler parameter to sd_event_add_signal() is NULL, and the
65       event source fires, this will be considered a request to exit the event
66       loop. In this case, the userdata parameter, cast to an integer, is
67       passed as the exit code parameter to sd_event_exit(3).
68
69       sd_event_source_get_signal() returns the configured signal number of an
70       event source created previously with sd_event_add_signal(). It takes
71       the event source object as the source parameter.
72

RETURN VALUE

74       On success, these functions return 0 or a positive integer. On failure,
75       they return a negative errno-style error code.
76
77   Errors
78       Returned errors may indicate the following problems:
79
80       -ENOMEM
81           Not enough memory to allocate an object.
82
83       -EINVAL
84           An invalid argument has been passed.
85
86       -EBUSY
87           A handler is already installed for this signal or the signal was
88           not blocked previously.
89
90       -ESTALE
91           The event loop is already terminated.
92
93       -ECHILD
94           The event loop has been created in a different process.
95
96       -EDOM
97           The passed event source is not a signal event source.
98

NOTES

100       These APIs are implemented as a shared library, which can be compiled
101       and linked to with the libsystemd pkg-config(1) file.
102

SEE ALSO

104       systemd(1), sd-event(3), sd_event_new(3), sd_event_now(3),
105       sd_event_add_io(3), sd_event_add_time(3), sd_event_add_child(3),
106       sd_event_add_inotify(3), sd_event_add_defer(3),
107       sd_event_source_set_enabled(3), sd_event_source_set_description(3),
108       sd_event_source_set_userdata(3), sd_event_source_set_floating(3),
109       signal(7), signalfd(2), sigprocmask(2), pthread_sigmask(3)
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113systemd 251                                             SD_EVENT_ADD_SIGNAL(3)
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