1SD_BUS_MESSAGE_READ_BASIC(3)sd_bus_message_read_basiScD_BUS_MESSAGE_READ_BASIC(3)
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NAME

6       sd_bus_message_read_basic - Read a basic type from a message
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SYNOPSIS

9       #include <systemd/sd-bus.h>
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11       int sd_bus_message_read_basic(sd_bus_message *m, char type, void *p);
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DESCRIPTION

14       sd_bus_message_read_basic() reads a basic type from a message and
15       advances the read position in the message. The set of basic types and
16       their ascii codes passed in type are described in the D-Bus
17       Specification[1].
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19       If p is not NULL, it should contain a pointer to an appropriate object.
20       For example, if type is 'y', the object passed in p should have type
21       uint8_t *. If type is 's', the object passed in p should have type
22       const char **. Note that, if the basic type is a pointer (e.g., const
23       char * in the case of a string), the pointer is only borrowed and the
24       contents must be copied if they are to be used after the end of the
25       messages lifetime. Similarly, during the lifetime of such a pointer,
26       the message must not be modified. See the table below for a complete
27       list of allowed types.
28
29       Table 1. Item type specifiers
30       ┌──────────┬─────────────────────────┬──────────────────┬─────────────────┐
31       │Specifier │ Constant                │ Description      │ Expected C Type │
32       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
33       │"y"       │ SD_BUS_TYPE_BYTE        │ unsigned integer │ uint8_t *       │
34       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
35       │"b"       │ SD_BUS_TYPE_BOOLEAN     │ boolean          │ int *           │
36       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
37       │"n"       │ SD_BUS_TYPE_INT16       │ signed integer   │ int16_t *       │
38       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
39       │"q"       │ SD_BUS_TYPE_UINT16      │ unsigned integer │ uint16_t *      │
40       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
41       │"i"       │ SD_BUS_TYPE_INT32       │ signed integer   │ int32_t *       │
42       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
43       │"u"       │ SD_BUS_TYPE_UINT32      │ unsigned integer │ uint32_t *      │
44       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
45       │"x"       │ SD_BUS_TYPE_INT64       │ signed integer   │ int64_t *       │
46       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
47       │"t"       │ SD_BUS_TYPE_UINT64      │ unsigned integer │ uint64_t *      │
48       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
49       │"d"       │ SD_BUS_TYPE_DOUBLE      │ floating-point   │ double *        │
50       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
51       │"s"       │ SD_BUS_TYPE_STRING      │ Unicode string   │ const char **   │
52       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
53       │"o"       │ SD_BUS_TYPE_OBJECT_PATH │ object path      │ const char **   │
54       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
55       │"g"       │ SD_BUS_TYPE_SIGNATURE   │ signature        │ const char **   │
56       ├──────────┼─────────────────────────┼──────────────────┼─────────────────┤
57       │"h"       │ SD_BUS_TYPE_UNIX_FD     │ UNIX file        │ int *           │
58       │          │                         │ descriptor       │                 │
59       └──────────┴─────────────────────────┴──────────────────┴─────────────────┘
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61       If there is no object of the specified type at the current position in
62       the message, an error is returned.
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RETURN VALUE

65       On success, sd_bus_message_read_basic() returns 0 or a positive
66       integer. On failure, it returns a negative errno-style error code.
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68   Errors
69       Returned errors may indicate the following problems:
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71       -EINVAL
72           Specified type string is invalid or the message parameter is NULL.
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74       -ENXIO
75           The message does not contain the specified type at current
76           position.
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78       -EBADMSG
79           The message cannot be parsed.
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SEE ALSO

82       systemd(1), sd-bus(3), sd_bus_message_append_basic(3),
83       sd_bus_message_skip(3), sd_bus_message_read(3)
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NOTES

86        1. D-Bus Specification
87           https://dbus.freedesktop.org/doc/dbus-specification.html
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91systemd 243                                       SD_BUS_MESSAGE_READ_BASIC(3)
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