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128 lines
4.3 KiB
Groff
128 lines
4.3 KiB
Groff
'\" t
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.TH "SD_EVENT_ADD_CHILD" "3" "" "systemd 219" "sd_event_add_child"
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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_child, sd_event_source_get_child_pid \- Add a child state change 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_child('u
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.BI "int sd_event_add_child(sd_event\ *" "event" ", sd_event_source\ **" "source" ", pid_t\ " "pid" ", int\ " "options" ", sd_event_child_handler_t\ " "handler" ", void\ *" "userdata" ");"
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.HP \w'typedef\ int\ (*sd_event_child_handler_t)('u
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.BI "typedef int (*sd_event_child_handler_t)(sd_event_source\ *" "s" ", const\ siginfo_t\ *" "si" ", void\ *" "userdata" ");"
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.HP \w'int\ sd_event_source_get_child_pid('u
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.BI "int sd_event_source_get_child_pid(sd_event_source\ *" "source" ", pid_t\ *" "pid" ");"
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.SH "DESCRIPTION"
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.PP
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\fBsd_event_add_child()\fR
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adds a new child state change 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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\fIpid\fR
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parameter specifies the process to watch\&. The
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\fIhandler\fR
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must reference a function to call when the process changes state\&. 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 siginfo_t
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structure containing the information about the event\&. The
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\fIoptions\fR
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parameter determines which state changes will be watched for\&. It must contain an OR\-ed mask of
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\fBWEXITED\fR
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(watch for the child terminating),
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\fBWSTOPPED\fR
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(watch for the child being stopped by a signal), and
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\fBWCONTINUED\fR
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(watch for the child being resumed by a signal)\&. See
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\fBwaitid\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 child\&. The handler is enabled for a single event (\fBSD_EVENT_ONESHOT\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_child_pid()\fR
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retrieves the configured
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\fIpid\fR
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of a child state change event source created previously with
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\fBsd_event_add_child()\fR\&. It takes the event source object as the
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\fIsource\fR
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parameter and a pointer to
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\fBpid_t\fR
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to return the result in\&.
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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\&. This includes specifying an empty mask in
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\fIoptions\fR
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or a mask which contains values different than a combination of
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\fBWEXITED\fR,
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\fBWSTOPPED\fR, and
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\fBWCONTINUED\fR\&.
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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 child\&.
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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_child()\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_signal\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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