sd_bus_message_get_cookie, sd_bus_message_get_reply_cookie - Returns the transaction cookie of a message
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.
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.
Returned errors may indicate the following problems:
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.