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)