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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | NOTES | COLOPHON |
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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.
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 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) 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 258~rc2 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)
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HTML rendering created 2025-09-06 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. |
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