|
HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | NOTES | COLOPHON |
|
|
|
SD_BUS_MESSAGE_NEW(3) sd_bus_message_new SD_BUS_MESSAGE_NEW(3)
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
#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);
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 internal reference counter of m
by one.
sd_bus_message_unref() decreases the internal 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.
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.
Functions described here are available as a shared library, which
can be compiled against and linked to with the
libsystemd pkg-config(1) file.
All functions listed here are thread-agnostic and only a single
thread may operate on a given object at any given time. Different
threads may access the same object at different times. Multiple
independent objects may be used from different threads in
parallel.
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.
sd_bus_message_new(), sd_bus_message_ref(),
sd_bus_message_unref(), sd_bus_message_unrefp(), and
sd_bus_message_get_bus() were added in version 240.
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)
1. Clean-up Variable Attribute
https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
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 2026-08-04. (At that
time, the date of the most recent commit that was found in the
repository was 2026-08-03.) 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 262~devel 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)
|
HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|