NAME
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 itSYNOPSIS
#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);
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 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"); } ... }
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() and sd_bus_flush_close_unref() always return NULL.Errors
Returned errors may indicate the following problems: -ENOMEMMemory allocation failed.
NOTES
These APIs are implemented 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), sd_bus_close(3)NOTES
- 1.
- Clean-up Variable Attribute
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