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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | NOTES | COLOPHON |
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SD_BUS_NEW(3) sd_bus_new SD_BUS_NEW(3)
sd_bus_new, sd_bus_ref, sd_bus_unref, sd_bus_unrefp,
sd_bus_close_unref, sd_bus_close_unrefp,
sd_bus_flush_close_unref, sd_bus_flush_close_unrefp - Create a
new bus object and create or destroy references to it
#include <systemd/sd-bus.h>
int sd_bus_new(sd_bus **bus);
sd_bus *sd_bus_ref(sd_bus *bus);
sd_bus *sd_bus_unref(sd_bus *bus);
sd_bus *sd_bus_close_unref(sd_bus *bus);
sd_bus *sd_bus_flush_close_unref(sd_bus *bus);
void sd_bus_unrefp(sd_bus **busp);
void sd_bus_close_unrefp(sd_bus **busp);
void sd_bus_flush_close_unrefp(sd_bus **busp);
sd_bus_new() creates a new bus object. This object is
reference-counted, and will be destroyed when all references are
gone. Initially, the caller of this function owns the sole
reference and the bus object will not be connected to any bus. To
connect it to a bus, make sure to set an address with
sd_bus_set_address(3) or a related call, and then start the
connection with sd_bus_start(3).
In most cases, it is better to use sd_bus_default_user(3),
sd_bus_default_system(3) or related calls instead of the more
low-level sd_bus_new() and sd_bus_start(). The higher-level
functions not only allocate a bus object but also start the
connection to a well-known bus in a single function call.
sd_bus_ref() increases the reference counter of bus by one.
sd_bus_unref() decreases the reference counter of bus by one.
Once the reference count has dropped to zero, bus is destroyed
and cannot be used anymore, so further calls to sd_bus_ref() or
sd_bus_unref() are illegal.
sd_bus_unrefp() is similar to sd_bus_unref() but takes a pointer
to a pointer to an sd_bus object. This call is useful in
conjunction with GCC's and LLVM's Clean-up Variable Attribute[1].
Note that this function is defined as an inline function. Use a
declaration like the following, in order to allocate a bus object
that is freed automatically as the code block is left:
{
__attribute__((cleanup(sd_bus_unrefp))) sd_bus *bus = NULL;
int r;
...
r = sd_bus_default(&bus);
if (r < 0) {
errno = -r;
fprintf(stderr, "Failed to allocate bus: %m\n");
}
...
}
sd_bus_ref() and sd_bus_unref() execute no operation if the
argument is NULL. sd_bus_unrefp() will first dereference its
argument, which must not be NULL, and will execute no operation
if that is NULL.
sd_bus_close_unref() is similar to sd_bus_unref(), but first
executes sd_bus_close(3), ensuring that the connection is
terminated before the reference to the connection is dropped and
possibly the object freed.
sd_bus_flush_close_unref() is similar to sd_bus_unref(), but
first executes sd_bus_flush(3) as well as sd_bus_close(3),
ensuring that any pending messages are synchronously flushed out
before the reference to the connection is dropped and possibly
the object freed. This call is particularly useful immediately
before exiting from a program as it ensures that any pending
outgoing messages are written out, and unprocessed but queued
incoming messages released before the connection is terminated
and released.
sd_bus_close_unrefp() is similar to sd_bus_close_unref(), but may
be used in GCC's and LLVM's Clean-up Variable Attribute, see
above. Similarly, sd_bus_flush_close_unrefp() is similar to
sd_bus_flush_close_unref().
On success, sd_bus_new() returns 0 or a positive integer. On
failure, it returns a negative errno-style error code.
sd_bus_ref() always returns the argument.
sd_bus_unref() and sd_bus_flush_close_unref() always return NULL.
Errors
Returned errors may indicate the following problems:
-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_new(), sd_bus_ref(), and sd_bus_unref() were added in
version 209.
sd_bus_unrefp() was added in version 229.
sd_bus_flush_close_unref() and sd_bus_flush_close_unrefp() were
added in version 240.
sd_bus_close_unref() and sd_bus_close_unrefp() were added in
version 241.
systemd(1), sd-bus(3), sd_bus_default_user(3),
sd_bus_default_system(3), sd_bus_open_user(3),
sd_bus_open_system(3), sd_bus_close(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 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) 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
[email protected]
systemd 257~devel SD_BUS_NEW(3)
Pages that refer to this page: sd-bus(3), sd_bus_close(3), sd_bus_default(3), sd_bus_message_get_cookie(3), sd_bus_message_get_monotonic_usec(3), sd_bus_message_new(3), sd_bus_message_set_destination(3), sd_bus_request_name(3), sd_bus_set_address(3), sd_bus_slot_ref(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2024-06-26 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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