SD_BUS_MESSAGE_METHOD_RETURN(3)

1SD_BUS_MESSAGE_NEW(3)         sd_bus_message_new         SD_BUS_MESSAGE_NEW(3)
2
3
4

NAME

6       sd_bus_message_new, sd_bus_message_ref, sd_bus_message_unref,
7       sd_bus_message_unrefp, SD_BUS_MESSAGE_METHOD_CALL,
8       SD_BUS_MESSAGE_METHOD_RETURN, SD_BUS_MESSAGE_METHOD_ERROR,
9       SD_BUS_MESSAGE_SIGNAL, sd_bus_message_get_bus - Create a new bus
10       message object and create or destroy references to it
11

SYNOPSIS

13       #include <systemd/sd-bus.h>
14
15       enum {
16             SD_BUS_MESSAGE_METHOD_CALL,
17             SD_BUS_MESSAGE_METHOD_RETURN,
18             SD_BUS_MESSAGE_METHOD_ERROR,
19             SD_BUS_MESSAGE_SIGNAL,
20       };
21
22       int sd_bus_message_new(sd_bus *bus, sd_bus_message **m, uint8_t type);
23
24       sd_bus_message *sd_bus_message_ref(sd_bus_message *m);
25
26       sd_bus_message *sd_bus_message_unref(sd_bus_message *m);
27
28       void sd_bus_message_unrefp(sd_bus_message **mp);
29
30       sd_bus *sd_bus_message_get_bus(sd_bus_message *m);
31

DESCRIPTION

33       sd_bus_message_new() creates a new bus message object attached to the
34       bus bus and returns it in the output parameter m. This object is
35       reference-counted, and will be destroyed when all references are gone.
36       Initially, the caller of this function owns the sole reference to the
37       message object. Note that the message object holds a reference to the
38       bus object, so the bus object will not be destroyed as long as the
39       message exists.
40
41       Note: this is a low-level call. In most cases functions like
42       sd_bus_message_new_method_call(3), sd_bus_message_new_method_error(3),
43       sd_bus_message_new_method_return(3), and sd_bus_message_new_signal(3)
44       that create a message of a certain type and initialize various fields
45       are easier to use.
46
47       The type parameter specifies the type of the message. It must be one of
48       SD_BUS_MESSAGE_METHOD_CALL — a method call,
49       SD_BUS_MESSAGE_METHOD_RETURN — a method call reply,
50       SD_BUS_MESSAGE_METHOD_ERROR — an error reply to a method call,
51       SD_BUS_MESSAGE_SIGNAL — a broadcast message with no reply.
52
53       The flag to allow interactive authorization is initialized based on the
54       current value set in the bus object, see
55       sd_bus_set_allow_interactive_authorization(3). This may be changed
56       using sd_bus_message_set_allow_interactive_authorization(3).
57
58       sd_bus_message_ref() increases the internal reference counter of m by
59       one.
60
61       sd_bus_message_unref() decreases the internal reference counter of m by
62       one. Once the reference count has dropped to zero, message object is
63       destroyed and cannot be used anymore, so further calls to
64       sd_bus_message_ref() or sd_bus_message_unref() are illegal.
65
66       sd_bus_message_unrefp() is similar to sd_bus_message_unref() but takes
67       a pointer to a pointer to an sd_bus_message object. This call is useful
68       in conjunction with GCC's and LLVM's Clean-up Variable Attribute[1].
69       See sd_bus_new(3) for an example how to use the cleanup attribute.
70
71       sd_bus_message_ref() and sd_bus_message_unref() execute no operation if
72       the passed in bus message object address is NULL.
73       sd_bus_message_unrefp() will first dereference its argument, which must
74       not be NULL, and will execute no operation if that is NULL.
75
76       sd_bus_message_get_bus() returns the bus object that message m is
77       attached to.
78

RETURN VALUE

80       On success, sd_bus_message_new() returns 0 or a positive integer. On
81       failure, it returns a negative errno-style error code.
82
83       sd_bus_message_ref() always returns the argument.
84
85       sd_bus_message_unref() always returns NULL.
86
87       sd_bus_message_get_bus() always returns the bus object.
88
89   Errors
90       Returned errors may indicate the following problems:
91
92       -EINVAL
93           Specified type is invalid.
94
95       -ENOTCONN
96           The bus parameter bus is NULL or the bus is not connected.
97
98       -ENOMEM
99           Memory allocation failed.
100

NOTES

102       Functions described here are available as a shared library, which can
103       be compiled against and linked to with the libsystemd pkg-config(1)
104       file.
105
106       The code described here uses getenv(3), which is declared to be not
107       multi-thread-safe. This means that the code calling the functions
108       described here must not call setenv(3) from a parallel thread. It is
109       recommended to only do calls to setenv() from an early phase of the
110       program when no other threads have been started.
111

NOTES

118        1. Clean-up Variable Attribute
119           https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
120
121
122
123systemd 254                                              SD_BUS_MESSAGE_NEW(3)

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

NOTES

SEE ALSO

NOTES