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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |SEE ALSO |NOTES |COLOPHON | |
SD_BUS_...ND_ARRAY(3) sd_bus_message_append_arraySD_BUS_...ND_ARRAY(3)sd_bus_message_append_array, sd_bus_message_append_array_memfd, sd_bus_message_append_array_iovec, sd_bus_message_append_array_space - Append an array of fields to a D-Bus message
#include <systemd/sd-bus.h>int sd_bus_message_append_array(sd_bus_message *m, chartype,const void *ptr, size_tsize);int sd_bus_message_append_array_memfd(sd_bus_message *m,chartype, intmemfd,uint64_toffset,uint64_tsize);int sd_bus_message_append_array_iovec(sd_bus_message *m,chartype,const struct iovec *iov,unsignedn);int sd_bus_message_append_array_space(sd_bus_message *m,chartype, size_tsize,void **ptr);
Thesd_bus_message_append_array()function appends an array to a D-Bus messagem. A container will be opened, the array contents appended, and the container closed. The parametertype determines how the pointerp is interpreted.type must be one of the "trivial" types "y", "n", "q", "i", "u", "x", "t", "d" (but not "b"), as defined by theBasic D-Bus Types[1] section of the D-Bus specification, and listed insd_bus_message_append_basic(3). Pointerp must point to an array of sizesize bytes containing items of the respective type. Sizesize must be a multiple of the size of the typetype. As a special case,p may beNULL, ifsize is 0. The memory pointed to byp is copied into the memory area containing the message and stays in possession of the caller. The caller may hence freely change the data after this call without affecting the message the array was appended to. Thesd_bus_message_append_array_memfd()function appends an array of a trivial type to messagem, similar tosd_bus_message_append_array(). The contents of the memory file descriptormemfd starting at the specified offset and of the specified size is used as the contents of the array. The offset and size must be a multiple of the size of the typetype. However, as a special exception, if the offset is specified as zero and the size specified as UINT64_MAX the full memory file descriptor contents is used. The memory file descriptor is sealed by this call if it has not been sealed yet, and cannot be modified after this call. Seememfd_create(2) for details about memory file descriptors. Appending arrays with memory file descriptors enables efficient zero-copy data transfer, as the memory file descriptor may be passed as-is to the destination, without copying the memory in it to the destination process. Not all protocol transports support passing memory file descriptors between participants, in which case this call will automatically fall back to copying. Also, as memory file descriptor passing is inefficient for smaller amounts of data, copying might still be enforced even where memory file descriptor passing is supported. Thesd_bus_message_append_array_iovec()function appends an array of a trivial type to the messagem, similar tosd_bus_message_append_array(). Contents of the I/O vector arrayiov are used as the contents of the array. The total size ofiov payload (the sum ofiov_len fields) must be a multiple of the size of the typetype. Theiov argument must point ton I/O vector structures. Each structure may have the iov_base field set, in which case the memory pointed to will be copied into the message, or unset (set to zero), in which case a block of zeros of length iov_len bytes will be inserted. The memory pointed at byiov may be changed after this call. Thesd_bus_message_append_array_space()function appends space for an array of a trivial type to messagem. It behaves the same assd_bus_message_append_array(), but instead of copying items to the message, it returns a pointer to the destination area to the caller in pointerp. The caller should subsequently write the array contents to this memory. Modifications to the memory pointed to should only occur until the next operation on the bus message is invoked. Most importantly, the memory should not be altered anymore when another field has been added to the message or the message has been sealed.
On success, these calls return 0 or a positive integer. On failure, they return 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_append(3),sd_bus_message_append_basic(3),memfd_create(2),The D-Busspecification[2]
1. Basic D-Bus 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_ARRAY(3)Pages that refer to this page:sd-bus(3), sd_bus_message_append(3), sd_bus_message_append_strv(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. | |