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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | NOTES | COLOPHON |
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SD_BUS_...ND_BASIC(3) sd_bus_message_append_basic SD_BUS_...ND_BASIC(3)
sd_bus_message_append_basic - Attach a single field to a message
#include <systemd/sd-bus.h>
int sd_bus_message_append_basic(sd_bus_message *m, char type,
const void *p);
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 │ 1 byte │ uint8_t │
│ │ │ integer │ │ │
├───────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│ "b" │ SD_BUS_TYPE_BOOLEAN │ boolean │ 4 bytes │ int │
├───────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│ "n" │ SD_BUS_TYPE_INT16 │ signed │ 2 bytes │ int16_t │
│ │ │ integer │ │ │
├───────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│ "q" │ SD_BUS_TYPE_UINT16 │ unsigned │ 2 bytes │ uint16_t │
│ │ │ integer │ │ │
├───────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│ "i" │ SD_BUS_TYPE_INT32 │ signed │ 4 bytes │ int32_t │
│ │ │ integer │ │ │
├───────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│ "u" │ SD_BUS_TYPE_UINT32 │ unsigned │ 4 bytes │ uint32_t │
│ │ │ integer │ │ │
├───────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│ "x" │ SD_BUS_TYPE_INT64 │ signed │ 8 bytes │ int64_t │
│ │ │ integer │ │ │
├───────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│ "t" │ SD_BUS_TYPE_UINT64 │ unsigned │ 8 bytes │ uint64_t │
│ │ │ integer │ │ │
├───────────┼─────────────────────────┼────────────────┼──────────┼────────────┤
│ "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.
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.
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.
systemd(1), sd-bus(3), sd_bus_message_read_basic(3),
sd_bus_message_append(3), The D-Bus specification[2]
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
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 258~rc2 SD_BUS_...ND_BASIC(3)
Pages that refer to this page: sd-bus(3), sd_bus_message_append(3), sd_bus_message_append_array(3), sd_bus_message_append_string_memfd(3), sd_bus_message_append_strv(3), sd_bus_message_read_basic(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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