Movatterモバイル変換

sd_varlink_send(3) — Linux manual page

SD_VARLINK_SEND(3)           sd_varlink_sendSD_VARLINK_SEND(3)

NAME        top

       sd_varlink_send, sd_varlink_sendb, sd_varlink_sendbo - Enqueues a       Varlink method call, not expecting a reply

SYNOPSIS        top

#include <systemd/sd-varlink.h>int sd_varlink_send(sd_varlink *link, const char *method,sd_json_variant *parameters);int sd_varlink_sendb(sd_varlink *link, const char *method, ...);int sd_varlink_sendbo(sd_varlink *link, const char *method, ...);

DESCRIPTION        top

sd_varlink_send()submits a method call via a Varlink connection.       It takes the Varlink connection object, a method name as string       parameter, and a JSON object containing the parameters to pass as       function parameters. This call is asynchronous: the message will       not be delivered immediately but only oncesd_varlink_process(3)       is invoked (which will happen automatically in one of the       following event loop iterations if the Varlink connection is       attached to an even loop).sd_varlink_sendb()is similar tosd_varlink_send(), but instead of       expecting a fully constructedsd_json_variantobject carrying the       parameters, this object is constructed on-the-fly directly from       the parameter list, in a style identical tosd_json_build(3).sd_varlink_sendbo()is identical tosd_varlink_sendb(), but an       enclosing object is implicitly added, so that the parameter list       is expected to consist of field pairs only. For details about the       expected argument list, seesd_json_buildo(3).       Usesd_varlink_send(),sd_varlink_sendb()andsd_varlink_sendbo()       only if no method call results are required, as they neither       provide return parameters nor success/failure information. Usesd_varlink_call(3) (and related calls) to submit a method call       synchronously, returning the server's response.

RETURN VALUE        top

       On success,sd_varlink_send(),sd_varlink_sendb()andsd_varlink_sendbo()return a non-negative integer. On failure,       they return a negative errno-style error code.Errors       Returned errors may indicate the following problems:-EINVAL           An argument is invalid.-ENOMEM           Memory allocation failed.-ENOTCONN           The Varlink connection object is not connected.-EBUSY           The Varlink connection object is already used for other           purposes, i.e. executing a method call or similar.-ENOBUFS           The internal limit of queued messages for the Varlink           connection has been reached. This limit is set very high, and           hitting it typically indicates that the Varlink connection           object is stalled — possibly becausesd_varlink_process()has           not been called regularly enough, or because the peer is not           processing any queued messages. This limit is a safety           precaution to ensure a stalled peer will not result in           unbounded memory allocations on the client side.

NOTES        top

       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.

HISTORY        top

sd_varlink_send(),sd_varlink_sendb(),sd_varlink_sendbo()were       added in version 257.

SEE ALSO        top

systemd(1),sd-varlink(3),sd_varlink_call(3),sd_varlink_build(3)

COLOPHON        top

       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_VARLINK_SEND(3)

Pages that refer to this page: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.