|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | NOTES | COLOPHON |
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 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)
fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r));
...
}
sd_bus_ref() and sd_bus_unref() execute no operation if the passed in
bus object address 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.
These APIs are implemented as a shared library, which can be compiled
and linked to with the libsystemd pkg-config(1) file.
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 2020-08-13. (At that
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itory was 2020-08-11.) If you discover any rendering problems in
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more up-to-date source for the page, or you have corrections or
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of the original manual page), send a mail to man-pages@man7.org
systemd 246 SD_BUS_NEW(3)
Pages that refer to this page: sd_bus_close(3) , sd_bus_default_flush_close(3) , sd_bus_flush(3) , 30-systemd-environment-d-generator(7) , systemd.index(7)