sd_bus_message_new(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | NOTES | COLOPHON

SD_BUS_MESSAGE_NEW(3)      sd_bus_message_new      SD_BUS_MESSAGE_NEW(3)

NAME         top

       sd_bus_message_new, sd_bus_message_ref, sd_bus_message_unref,
       sd_bus_message_unrefp, SD_BUS_MESSAGE_METHOD_CALL,
       SD_BUS_MESSAGE_METHOD_RETURN, SD_BUS_MESSAGE_METHOD_ERROR,
       SD_BUS_MESSAGE_SIGNAL, sd_bus_message_get_bus - Create a new bus
       message object and create or destroy references to it

SYNOPSIS         top

       #include <systemd/sd-bus.h>

       enum {
             SD_BUS_MESSAGE_METHOD_CALL,
             SD_BUS_MESSAGE_METHOD_RETURN,
             SD_BUS_MESSAGE_METHOD_ERROR,
             SD_BUS_MESSAGE_SIGNAL,
       };

       int sd_bus_message_new(sd_bus *bus, sd_bus_message **m,
                              uint8_t type);

       sd_bus_message *sd_bus_message_ref(sd_bus_message *m);

       sd_bus_message *sd_bus_message_unref(sd_bus_message *m);

       void sd_bus_message_unrefp(sd_bus_message **mp);

       sd_bus *sd_bus_message_get_bus(sd_bus_message *m);

DESCRIPTION         top

       sd_bus_message_new() creates a new bus message object attached to
       the bus bus and returns it in the output parameter m. This object
       is reference-counted, and will be destroyed when all references
       are gone. Initially, the caller of this function owns the sole
       reference to the message object. Note that the message object
       holds a reference to the bus object, so the bus object will not
       be destroyed as long as the message exists.

       Note: this is a low-level call. In most cases functions like
       sd_bus_message_new_method_call(3),
       sd_bus_message_new_method_error(3),
       sd_bus_message_new_method_return(3), and
       sd_bus_message_new_signal(3) that create a message of a certain
       type and initialize various fields are easier to use.

       The type parameter specifies the type of the message. It must be
       one of SD_BUS_MESSAGE_METHOD_CALL — a method call,
       SD_BUS_MESSAGE_METHOD_RETURN — a method call reply,
       SD_BUS_MESSAGE_METHOD_ERROR — an error reply to a method call,
       SD_BUS_MESSAGE_SIGNAL — a broadcast message with no reply.

       The flag to allow interactive authorization is initialized based
       on the current value set in the bus object, see
       sd_bus_set_allow_interactive_authorization(3). This may be
       changed using
       sd_bus_message_set_allow_interactive_authorization(3).

       sd_bus_message_ref() increases the reference counter of m by one.

       sd_bus_message_unref() decreases the reference counter of m by
       one. Once the reference count has dropped to zero, message object
       is destroyed and cannot be used anymore, so further calls to
       sd_bus_message_ref() or sd_bus_message_unref() are illegal.

       sd_bus_message_unrefp() is similar to sd_bus_message_unref() but
       takes a pointer to a pointer to an sd_bus_message object. This
       call is useful in conjunction with GCC's and LLVM's Clean-up
       Variable Attribute[1]. See sd_bus_new(3) for an example how to
       use the cleanup attribute.

       sd_bus_message_ref() and sd_bus_message_unref() execute no
       operation if the passed in bus message object address is NULL.
       sd_bus_message_unrefp() will first dereference its argument,
       which must not be NULL, and will execute no operation if that is
       NULL.

       sd_bus_message_get_bus() returns the bus object that message m is
       attached to.

RETURN VALUE         top

       On success, sd_bus_message_new() returns 0 or a positive integer.
       On failure, it returns a negative errno-style error code.

       sd_bus_message_ref() always returns the argument.

       sd_bus_message_unref() always returns NULL.

       sd_bus_message_get_bus() always returns the bus object.

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           Specified type is invalid.

       -ENOTCONN
           The bus parameter bus is NULL or the bus is not connected.

       -ENOMEM
           Memory allocation failed.

NOTES         top

       These APIs are implemented 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_new(3),
       sd_bus_message_new_method_call(3),
       sd_bus_message_new_method_error(3),
       sd_bus_message_new_method_return(3), sd_bus_message_new_signal(3)

NOTES         top

        1. Clean-up Variable Attribute
           https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html

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 page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2020-12-18.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2020-12-18.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

systemd 247                                        SD_BUS_MESSAGE_NEW(3)

Pages that refer to this page: sd-bus(3)sd_bus_add_match(3)sd_bus_call(3)sd_bus_message_get_signature(3)sd_bus_message_get_type(3)sd_bus_process(3)sd_bus_slot_ref(3)systemd.directives(7)systemd.index(7)