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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |SEE ALSO |NOTES |COLOPHON | |
SD_BUS_...ND_BASIC(3) sd_bus_message_append_basicSD_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, chartype,const void *p);
sd_bus_message_append_basic()appends a single field to the messagem. The parametertype determines how the pointerp is interpreted.type must be one of the basic types as defined by theBasic 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. Iftype 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 parameterp is interpreted as a pointer to aNUL-terminated character sequence. As a special case, aNULLpointer 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 thelibsystemd pkg-config(1) file. The code described here usesgetenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not callsetenv(3) from a parallel thread. It is recommended to only do calls tosetenv()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 Typeshttps://dbus.freedesktop.org/doc/dbus-specification.html#basic-types 2. The D-Bus specificationhttps://dbus.freedesktop.org/doc/dbus-specification.html
This page is part of thesystemd (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 isnot part of the original manual page), send a mail to man-pages@man7.orgsystemd 258~rc2SD_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)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |