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

SD_BUS_NEW(3)                    sd_bus_new                    SD_BUS_NEW(3)

NAME         top

       sd_bus_new, sd_bus_ref, sd_bus_unref, sd_bus_unrefp - Create a new
       bus object and create or destroy references to it

SYNOPSIS         top

       #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);

       void sd_bus_unrefp(sd_bus **bus);

DESCRIPTION         top

       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 a better idea to invoke 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 calls not
       only allocate a bus object but also start the connection to a
       well-known bus in a single function invocation.

       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(), sd_bus_unref() and sd_bus_unrefp() execute no operation
       if the passed in bus object is NULL.

RETURN VALUE         top

       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() always returns NULL.

ERRORS         top

       Returned errors may indicate the following problems:

       -ENOMEM
           Memory allocation failed.

NOTES         top

       sd_bus_new() and other functions described here are available 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_default_user(3),
       sd_bus_default_system(3), sd_bus_open_user(3), sd_bus_open_system(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 2017-04-25.  If you dis‐
       cover 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 233                                                    SD_BUS_NEW(3)

Pages that refer to this page: sd-bus(3)sd_bus_default(3)sd_bus_message_get_cookie(3)sd_bus_message_get_monotonic_usec(3)sd_bus_request_name(3)systemd.directives(7)systemd.index(7)