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