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

       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.

HISTORY

       sd_bus_message_get_cookie() and sd_bus_message_get_reply_cookie() were added in version 209.

SEE ALSO

       systemd(1), sd-bus(3), sd_bus_new(3)