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