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115 lines
4.1 KiB
Groff
115 lines
4.1 KiB
Groff
'\" t
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.TH "SD_EVENT_ADD_SIGNAL" "3" "" "systemd 219" "sd_event_add_signal"
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.\" -----------------------------------------------------------------
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.\" * Define some portability stuff
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.\" -----------------------------------------------------------------
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.\" http://bugs.debian.org/507673
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.ie \n(.g .ds Aq \(aq
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.el .ds Aq '
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.\" -----------------------------------------------------------------
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.\" * set default formatting
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.\" -----------------------------------------------------------------
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.\" disable hyphenation
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.nh
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.\" disable justification (adjust text to left margin only)
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.ad l
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.\" -----------------------------------------------------------------
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.\" * MAIN CONTENT STARTS HERE *
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.\" -----------------------------------------------------------------
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.SH "NAME"
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sd_event_add_signal, sd_event_source_get_signal \- Add a signal event source to an event loop
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.SH "SYNOPSIS"
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.sp
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.ft B
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.nf
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#include <systemd/sd\-bus\&.h>
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.fi
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.ft
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.HP \w'int\ sd_event_add_signal('u
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.BI "int sd_event_add_signal(sd_event\ *" "event" ", sd_event_source\ **" "source" ", int\ " "signal" ", sd_event_signal_handler_t\ " "handler" ", void\ *" "userdata" ");"
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.HP \w'typedef\ int\ (*sd_event_signal_handler_t)('u
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.BI "typedef int (*sd_event_signal_handler_t)(sd_event_source\ *" "s" ", const\ struct\ signalfd_siginfo\ *" "si" ", void\ *" "userdata" ");"
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.HP \w'int\ sd_event_source_get_signal('u
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.BI "int sd_event_source_get_signal(sd_event_source\ *" "source" ");"
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.SH "DESCRIPTION"
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.PP
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\fBsd_event_add_signal()\fR
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adds a new signal event source to an event loop object\&. The event loop is specified in
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\fIevent\fR, the event source is returned in the
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\fIsource\fR
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parameter\&. The
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\fIsignal\fR
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parameter specifies the signal to be handled (see
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\fBsignal\fR(7))\&. The
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\fIhandler\fR
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must reference a function to call when the signal is delivered or be
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\fBNULL\fR\&. The handler function will be passed the
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\fIuserdata\fR
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pointer, which may be chosen freely by the caller\&. The handler also receives a pointer to a
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const struct signalfd_siginfo
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containing the information about the received signal\&. See
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\fBsignalfd\fR(2)
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for further information\&.
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.PP
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Only a single handler may be installed for a specific signal\&. The signal will be unblocked, and must be blocked when the function is called\&. If the handler is not specified (\fIhandler\fR
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is
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\fBNULL\fR), a default handler which causes the program to exit will be used\&. By default, the handler is enabled permanently (\fBSD_EVENT_ON\fR), but this may be changed with
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\fBsd_event_source_set_enabled\fR(3)\&. If the handler function returns a negative error code, it will be disabled after the invocation, even if
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\fBSD_EVENT_ON\fR
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mode is set\&.
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.PP
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\fBsd_event_source_get_signal()\fR
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retrieves the configured signal number of a signal event source created previously with
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\fBsd_event_add_signal()\fR\&. It takes the event source object as the
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\fIsource\fR
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parameter\&.
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.SH "RETURN VALUE"
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.PP
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On success, these functions return 0 or a positive integer\&. On failure, they return a negative errno\-style error code\&.
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.SH "ERRORS"
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.PP
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Returned errors may indicate the following problems:
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.PP
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\fB\-ENOMEM\fR
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.RS 4
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Not enough memory to allocate an object\&.
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.RE
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.PP
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\fB\-EINVAL\fR
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.RS 4
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An invalid argument has been passed\&.
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.RE
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.PP
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\fB\-EBUSY\fR
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.RS 4
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An handler is already installed for this signal or the signal was not blocked previously\&.
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.RE
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.PP
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\fB\-ESTALE\fR
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.RS 4
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The event loop is already terminated\&.
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.RE
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.PP
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\fB\-ECHILD\fR
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.RS 4
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The event loop has been created in a different process\&.
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.RE
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.SH "NOTES"
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.PP
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\fBsd_event_add_signal()\fR
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and the other functions described here are available as a shared library, which can be compiled and linked to with the
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\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
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file\&.
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.SH "SEE ALSO"
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.PP
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\fBsystemd\fR(1),
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\fBsd-event\fR(3),
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\fBsd_event_new\fR(3),
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\fBsd_event_add_time\fR(3),
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\fBsd_event_add_child\fR(3),
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\fBsd_event_add_defer\fR(3),
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\fBsd_event_source_set_enabled\fR(3)
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