SD_BUS_MESSAGE_GET_COOKIE

Section: sd_bus_message_get_cookie (3)
Updated:
Page Index

NAME

sd_bus_message_get_cookie, sd_bus_message_get_reply_cookie - Returns the transaction cookie of a message

SYNOPSIS

#include <systemd/sd-bus.h>

int sd_bus_message_get_cookie(sd_bus_message *message, uint64_t *cookie);
int sd_bus_message_get_reply_cookie(sd_bus_message *message, uint64_t *cookie);

DESCRIPTION

sd_bus_message_get_cookie()

returns the transaction cookie of a message. The cookie uniquely identifies a message within each bus peer, but is not globally unique. It is assigned when a message is sent.

sd_bus_message_get_reply_cookie() returns the transaction cookie of the message the specified message is a response to. When a reply message is generated for a method call message, its cookie is copied over into this field. Note that while every message that is transferred is identified by a cookie, only response messages carry a reply cookie field.

Both functions take a message object as first parameter and a place to store the 64-bit cookie in.

RETURN VALUE

On success, these calls return 0 or a positive integer. On failure, they return a negative errno-style error code.

On success, the cookie/reply cookie is returned in the specified 64-bit unsigned integer variable.

Errors

Returned errors may indicate the following problems:

-EINVAL

: A specified parameter is invalid.

-ENODATA

: No cookie has been assigned to this message. This either indicates that the message has not been sent yet and hence has no cookie assigned, or that the message is not a method response message and hence carries a reply cookie field.

NOTES

These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.