sd_event_add_signal(3) - Linux manual page (original) (raw)

SDEVENTADDSIGNAL(3) sd_event_add_signal SDEVENTADDSIGNAL(3)

NAME top

   sd_event_add_signal, sd_event_source_get_signal,
   sd_event_signal_handler_t, SD_EVENT_SIGNAL_PROCMASK - Add a UNIX
   process signal event source to an event loop

SYNOPSIS top

   **#include <systemd/sd-event.h>**

   **typedef struct sd_event_source sd_event_source;**

   **SD_EVENT_SIGNAL_PROCMASK**

   **typedef int (*sd_event_signal_handler_t)(sd_event_source ***_s_**,**
                                            **const struct signalfd_siginfo ***_si_**,**
                                            **void ***_userdata_**);**

   **int sd_event_add_signal(sd_event ***_event_**, sd_event_source** _source_**,**
                           **int** _signal_**,**
                           **sd_event_signal_handler_t** _handler_**,**
                           **void ***_userdata_**);**

   **int sd_event_source_get_signal(sd_event_source ***_source_**);**

DESCRIPTION top

   **sd_event_add_signal()** adds a new UNIX process signal event source
   to an event loop. The event loop object is specified in the _event_
   parameter, and the event source object is returned in the _source_
   parameter. The _signal_ parameter specifies the numeric signal to be
   handled (see [signal(7)](../man7/signal.7.html)).

   The _handler_ parameter is a function to call when the signal is
   received or **NULL**. The handler function will be passed the _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)](../man2/signalfd.2.html) for further
   information. The handler may return negative to signal an error
   (see below), other return values are ignored. If _handler_ is **NULL**,
   a default handler that calls [sd_event_exit(3)](../man3/sd%5Fevent%5Fexit.3.html) will be used.

   Only a single handler may be installed for a specific signal. The
   signal must be blocked in all threads before this function is
   called (using [sigprocmask(2)](../man2/sigprocmask.2.html) or [pthread_sigmask(3)](../man3/pthread%5Fsigmask.3.html)). For
   convenience, if the special flag **SD_EVENT_SIGNAL_PROCMASK** is ORed
   into the specified signal the signal will be automatically masked
   as necessary, for the calling thread. Note that this only works
   reliably if the signal is already masked in all other threads of
   the process, or if there are no other threads at the moment of
   invocation.

   By default, the event source is enabled permanently (**SD_EVENT_ON**),
   but this may be changed with [sd_event_source_set_enabled(3)](../man3/sd%5Fevent%5Fsource%5Fset%5Fenabled.3.html). If
   the handler function returns a negative error code, it will either
   be disabled after the invocation, even if the **SD_EVENT_ON** mode was
   requested before, or it will cause the loop to terminate, see
   [sd_event_source_set_exit_on_failure(3)](../man3/sd%5Fevent%5Fsource%5Fset%5Fexit%5Fon%5Ffailure.3.html).

   To destroy an event source object use [sd_event_source_unref(3)](../man3/sd%5Fevent%5Fsource%5Funref.3.html),
   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
   [sd_event_source_set_enabled(3)](../man3/sd%5Fevent%5Fsource%5Fset%5Fenabled.3.html) with **SD_EVENT_OFF**.

   If the second parameter of **sd_event_add_signal()** is **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.

   If the _handler_ parameter to **sd_event_add_signal()** is **NULL**, and the
   event source fires, this will be considered a request to exit the
   event loop. In this case, the _userdata_ parameter, cast to an
   integer, is passed as the exit code parameter to [sd_event_exit(3)](../man3/sd%5Fevent%5Fexit.3.html).

   **sd_event_source_get_signal()** returns the configured signal number
   of an event source created previously with **sd_event_add_signal()**.
   It takes the event source object as the _source_ parameter.

RETURN VALUE top

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

Errors Returned errors may indicate the following problems:

   **-ENOMEM**
       Not enough memory to allocate an object.

   **-EINVAL**
       An invalid argument has been passed.

   **-EBUSY**
       A handler is already installed for this signal or the signal
       was not blocked previously.

   **-ESTALE**
       The event loop is already terminated.

   **-ECHILD**
       The event loop has been created in a different process,
       library or module instance.

   **-EDOM**
       The passed event source is not a signal event source.

NOTES top

   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)](../man3/getenv.3.html), which is declared to be
   not multi-thread-safe. This means that the code calling the
   functions described here must not call [setenv(3)](../man3/setenv.3.html) 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.

HISTORY top

   **sd_event_add_signal()**, **sd_event_signal_handler_t()**, and
   **sd_event_source_get_signal()** were added in version 217.

COLOPHON top

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   manager) project.  Information about the project can be found at
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systemd 258~devel SDEVENTADDSIGNAL(3)

sd_event_add_signal(3) - Linux manual page (original) (raw)

NAME top

SYNOPSIS top

DESCRIPTION top

RETURN VALUE top

NOTES top

HISTORY top

SEE ALSO top

COLOPHON top