x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_TRACK_ADD_NAME(3) sd_bus_track_add_name SD_BUS_TRACK_ADD_NAME(3)
NAME
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
SYNOPSIS
#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);
DESCRIPTION
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.
RETURN VALUE
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.
Errors
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.
NOTES
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), which is declared to be not
multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) 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.
SEE ALSO
systemd(1), sd-bus(3), sd_bus_track_new(3)
systemd 254 SD_BUS_TRACK_ADD_NAME(3)
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