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)

NAME         top

       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         top

       #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         top

       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         top

       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         top

       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         top

       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.

SEE ALSO         top

       systemd(1), sd-bus(3), sd_bus_track_new(3)

COLOPHON         top

       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)