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)). 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
37       Only a single handler may be installed for a specific signal. The
38       signal will be unblocked by this call, and must be blocked before this
39       function is called in all threads (using sigprocmask(2)). If the
40       handler is not specified (handler is NULL), a default handler which
41       causes the program to exit cleanly will be used.
42
43       By default, the event source is enabled permanently (SD_EVENT_ON), but
44       this may be changed with sd_event_source_set_enabled(3). If the handler
45       function returns a negative error code, it will be disabled after the
46       invocation, even if the SD_EVENT_ON mode was requested before.
47
48       To destroy an event source object use sd_event_source_unref(3), but
49       note that the event source is only removed from the event loop when all
50       references to the event source are dropped. To make sure an event
51       source does not fire anymore, even if it is still referenced, disable
52       the event source using sd_event_source_set_enabled(3) with
53       SD_EVENT_OFF.
54
55       If the second parameter of sd_event_add_signal() is NULL no reference
56       to the event source object is returned. In this case the event source
57       is considered "floating", and will be destroyed implicitly when the
58       event loop itself is destroyed.
59
60       sd_event_source_get_signal() returns the configured signal number of an
61       event source created previously with sd_event_add_signal(). It takes
62       the event source object as the source parameter.
63

RETURN VALUE

65       On success, these functions return 0 or a positive integer. On failure,
66       they return a negative errno-style error code.
67

ERRORS

69       Returned errors may indicate the following problems:
70
71       -ENOMEM
72           Not enough memory to allocate an object.
73
74       -EINVAL
75           An invalid argument has been passed.
76
77       -EBUSY
78           A handler is already installed for this signal or the signal was
79           not blocked previously.
80
81       -ESTALE
82           The event loop is already terminated.
83
84       -ECHILD
85           The event loop has been created in a different process.
86
87       -EDOM
88           The passed event source is not a signal event source.
89

NOTES

91       These APIs are implemented as a shared library, which can be compiled
92       and linked to with the libsystemd pkg-config(1) file.
93

SEE ALSO

95       systemd(1), sd-event(3), sd_event_new(3), sd_event_now(3),
96       sd_event_add_io(3), sd_event_add_time(3), sd_event_add_child(3),
97       sd_event_add_inotify(3), sd_event_add_defer(3),
98       sd_event_source_set_enabled(3), sd_event_source_set_description(3),
99       sd_event_source_set_userdata(3), signal(7), signalfd(2)
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103systemd 239                                             SD_EVENT_ADD_SIGNAL(3)
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