NAME

       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

       #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

       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

       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

       Returned errors may indicate the following problems:

       -ENOMEM
           Memory allocation failed.

NOTES

       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

       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

        1. Clean-up Variable Attribute
           https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html