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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | NOTES | SEE ALSO | COLOPHON |
SD_BUS_TRACK_ADD_NAME(3) sd_bus_track_add_name SD_BUS_TRACK_ADD_NAME(3)
sd_bus_track_add_name, sd_bus_track_add_sender,
sd_bus_track_remove_name, sd_bus_track_remove_sender,
sd_bus_track_count, sd_bus_track_count_sender,
sd_bus_track_count_name, sd_bus_track_contains, sd_bus_track_first,
sd_bus_track_next - Add, remove and retrieve bus peers tracked in a
bus peer tracking object
#include <systemd/sd-bus.h>
int sd_bus_track_add_name(sd_bus_track* t, const char* name);
int sd_bus_track_add_sender(sd_bus_track* t,
sd_bus_message* message);
int sd_bus_track_remove_name(sd_bus_track* t, const char* name);
int sd_bus_track_remove_sender(sd_bus_track* t,
sd_bus_message* message);
unsigned sd_bus_track_count(sd_bus_track* t);
int sd_bus_track_count_name(sd_bus_track* t, const char* name);
int sd_bus_track_count_sender(sd_bus_track* t,
sd_bus_message* message);
int sd_bus_track_contains(sd_bus_track* t, const char* name);
const char* sd_bus_track_first(sd_bus_track* t);
const char* sd_bus_track_next(sd_bus_track* t);
sd_bus_track_add_name() adds a peer to track to a bus peer tracking
object. The first argument should refer to a bus peer tracking object
created with sd_bus_track_new(3), the second name should refer to a
D-Bus peer name to track, either in unique or well-known service
format. If the name is not tracked yet it will be added to the list
of names to track. If it already is being tracked and non-recursive
mode is enabled, no operation is executed by this call. If recursive
mode is enabled a per-name counter is increased by one each time this
call is invoked, and sd_bus_track_remove_name() has to be called as
many times as sd_bus_track_add_name() was invoked before in order to
stop tracking of the name. Use sd_bus_track_set_recursive(3) to
switch from the default non-recursive mode to recursive mode, or
back. Note that the specified name is tracked as it is, well-known
names are not resolved to unique names by this call. Note that
multiple bus peer tracking objects may track the same name.
sd_bus_track_remove_name() undoes the effect of
sd_bus_track_add_name() and removes a bus peer name from the list of
peers to watch. Depending on whether non-recursive or recursive mode
is enabled for the bus peer tracking object this call will either
remove the name fully from the tracking object, or will simply
decrement the per-name counter by one, removing the name only when
the counter reaches zero (see above). Note that a bus peer
disconnecting from the bus will implicitly remove its names fully
from the bus peer tracking object, regardless of the current per-name
counter.
sd_bus_track_add_sender() and sd_bus_track_remove_sender() are
similar to sd_bus_track_add_name() and sd_bus_track_remove_name() but
take a bus message as argument. The sender of this bus message is
determined and added to/removed from the bus peer tracking object. As
messages always originate from unique names, and never from
well-known names this means that this call will effectively only add
unique names to the bus peer tracking object.
sd_bus_track_count() returns the number of names currently being
tracked by the specified bus peer tracking object. Note that this
function always returns the actual number of names tracked, and hence
if sd_bus_track_add_name() has been invoked multiple times for the
same name it is only counted as one, regardless if recursive mode is
used or not.
sd_bus_track_count_name() returns the current per-name counter for
the specified name. If non-recursive mode is used this returns either
1 or 0, depending on whether the specified name has been added to the
tracking object before, or not. If recursive mode has been enabled,
values larger than 1 may be returned too, in case
sd_bus_track_add_name() has been called multiple times for the same
name.
sd_bus_track_count_sender() is similar to sd_bus_track_count_name(),
but takes a bus message object and returns the per-name counter
matching the sender of the message.
sd_bus_track_contains() may be used to determine whether the
specified name has been added at least once to the specified bus peer
tracking object.
sd_bus_track_first() and sd_bus_track_next() may be used to enumerate
all names currently being tracked by the passed bus peer tracking
object. sd_bus_track_first() returns the first entry in the object,
and resets an internally maintained read index. Each subsequent
invocation of sd_bus_track_next() returns the next name contained in
the bus object. If the end is reached NULL is returned. If no names
have been added to the object yet sd_bus_track_first() will return
NULL immediately. The order in which names are returned is undefined;
in particular which name is considered the first returned is not
defined. If recursive mode is enabled and the same name has been
added multiple times to the bus peer tracking object it is only
returned once by this enumeration. If new names are added to or
existing names removed from the bus peer tracking object while it is
being enumerated the enumeration ends on the next invocation of
sd_bus_track_next() as NULL is returned.
On success, sd_bus_track_add_name() and sd_bus_track_add_sender()
return 0 if the specified name has already been added to the bus peer
tracking object before and positive if it hasn't. On failure, they
return a negative errno-style error code.
sd_bus_track_remove_name() and sd_bus_track_remove_sender() return
positive if the specified name was previously tracked by the bus peer
tracking object and has now been removed. In non-recursive mode, 0 is
returned if the specified name was not being tracked yet. In
recursive mode -EUNATCH is returned in this case. On failure, they
return a negative errno-style error code.
sd_bus_track_count() returns the number of names currently being
tracked, or 0 on failure.
sd_bus_track_count_name() and sd_bus_track_count_sender() return the
current per-name counter for the specified name or the sender of the
specified message. Zero is returned for names that are not being
tracked yet, a positive value for names added at least once. Larger
values than 1 are only returned in recursive mode. On failure, a
negative errno-style error code is returned.
sd_bus_track_contains() returns the passed name if it exists in the
bus peer tracking object. On failure, and if the name has not been
added yet NULL is returned.
sd_bus_track_first() and sd_bus_track_next() return the first/next
name contained in the bus peer tracking object, and NULL if the end
of the enumeration is reached and on error.
Returned errors may indicate the following problems:
-EUNATCH
sd_bus_track_remove_name() or sd_bus_track_remove_sender() have
been invoked for a name not previously added to the bus peer
object.
-EINVAL
Specified parameter is invalid.
-ENOMEM
Memory allocation failed.
sd_bus_track_add_name() and the other calls described here are
available as a shared library, which can be compiled and linked to
with the libsystemd pkg-config(1) file.
systemd(1), sd-bus(3), sd_bus_track_new(3)
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
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COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
systemd 234 SD_BUS_TRACK_ADD_NAME(3)
Pages that refer to this page: sd-bus(3), sd_bus_track_new(3), systemd.directives(7), systemd.index(7)