sd_bus_message_get_cookie - Man Page

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);

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

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.