NAME

       sd_bus_message_append_basic - Attach a single field to a message

SYNOPSIS

       #include <systemd/sd-bus.h>

       int sd_bus_message_append_basic(sd_bus_message *m, char type, const void *p);

DESCRIPTION

       sd_bus_message_append_basic() appends a single field to the message m. The parameter type
       determines how the pointer p is interpreted.  type must be one of the basic types as
       defined by the Basic Types[1] section of the D-Bus specification, and listed in the table
       below.

       Table 1. Item type specifiers
       ┌──────────┬─────────────────────────┬──────────────────┬──────────┬─────────────────┐
       │Specifier │ Constant                │ Description      │ Size     │ Expected C Type │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"y"       │ SD_BUS_TYPE_BYTE        │ unsigned integer │ 1 byte   │ uint8_t         │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"b"       │ SD_BUS_TYPE_BOOLEAN     │ boolean          │ 4 bytes  │ int             │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"n"       │ SD_BUS_TYPE_INT16       │ signed integer   │ 2 bytes  │ int16_t         │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"q"       │ SD_BUS_TYPE_UINT16      │ unsigned integer │ 2 bytes  │ uint16_t        │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"i"       │ SD_BUS_TYPE_INT32       │ signed integer   │ 4 bytes  │ int32_t         │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"u"       │ SD_BUS_TYPE_UINT32      │ unsigned integer │ 4 bytes  │ uint32_t        │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"x"       │ SD_BUS_TYPE_INT64       │ signed integer   │ 8 bytes  │ int64_t         │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"t"       │ SD_BUS_TYPE_UINT64      │ unsigned integer │ 8 bytes  │ uint64_t        │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"d"       │ SD_BUS_TYPE_DOUBLE      │ floating-point   │ 8 bytes  │ double          │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"s"       │ SD_BUS_TYPE_STRING      │ Unicode string   │ variable │ char[]          │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"o"       │ SD_BUS_TYPE_OBJECT_PATH │ object path      │ variable │ char[]          │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"g"       │ SD_BUS_TYPE_SIGNATURE   │ signature        │ variable │ char[]          │
       ├──────────┼─────────────────────────┼──────────────────┼──────────┼─────────────────┤
       │"h"       │ SD_BUS_TYPE_UNIX_FD     │ UNIX file        │ 4 bytes  │ int             │
       │          │                         │ descriptor       │          │                 │
       └──────────┴─────────────────────────┴──────────────────┴──────────┴─────────────────┘

       The value of the parameter is copied into a memory area held by the message object, stays
       in the possession of the caller and may hence be freely changed after this call without
       affecting the bus message it has been added to. If type is "h" (UNIX file descriptor), the
       descriptor is duplicated by this call and the passed descriptor stays in possession of the
       caller.

       For types "s", "o", and "g", the parameter p is interpreted as a pointer to a
       NUL-terminated character sequence. As a special case, a NULL pointer is interpreted as an
       empty string. The string should be valid Unicode string encoded as UTF-8. In case of the
       two latter types, the additional requirements for a D-Bus object path or type signature
       should be satisfied. Those requirements should be verified by the recipient of the
       message.

RETURN VALUE

       On success, this call returns 0 or a positive integer. On failure, it returns a negative
       errno-style error code.

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           Specified parameter is invalid.

       -EPERM
           Message has been sealed.

       -ESTALE
           Message is in invalid state.

       -ENXIO
           Message cannot be appended to.

       -ENOMEM
           Memory allocation failed.

NOTES

       Functions described here are available as a shared library, which can be compiled against
       and linked to with the libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be not multi-thread-safe.
       This means that the code calling the functions described here must not call setenv(3) from
       a parallel thread. It is recommended to only do calls to setenv() from an early phase of
       the program when no other threads have been started.

SEE ALSO

       systemd(1), sd-bus(3), sd_bus_message_read_basic(3), sd_bus_message_append(3), The D-Bus
       specification[2]

NOTES

        1. Basic Types
           https://dbus.freedesktop.org/doc/dbus-specification.html#basic-types

        2. The D-Bus specification
           https://dbus.freedesktop.org/doc/dbus-specification.html