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.

SEE ALSO

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