systemd Developer Lennart Poettering lennart@poettering.net sd_bus_message_get_cookie 3 sd_bus_message_get_cookie sd_bus_message_get_reply_cookie Returns the transaction cookie of a message #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 64bit cookie in. On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style error code. On success the cookie/reply cookie is returned in the specified 64bit unsigned integer variable. 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 to reply cookie field. The sd_bus_message_get_cookie() and sd_bus_message_get_reply_cookie() interfaces are available as a shared library, which can be compiled and linked to with the libsystemd-bus pkg-config1 file. systemd1, sd-bus3, sd_bus_new3