systemd sd_bus_message_new 3 sd_bus_message_new sd_bus_message_ref sd_bus_message_unref sd_bus_message_unrefp SD_BUS_MESSAGE_METHOD_CALL SD_BUS_MESSAGE_METHOD_RETURN SD_BUS_MESSAGE_METHOD_ERROR SD_BUS_MESSAGE_SIGNAL sd_bus_message_get_bus Create a new bus message object and create or destroy references to it #include <systemd/sd-bus.h> enum { SD_BUS_MESSAGE_METHOD_CALL, SD_BUS_MESSAGE_METHOD_RETURN, SD_BUS_MESSAGE_METHOD_ERROR, SD_BUS_MESSAGE_SIGNAL, }; int sd_bus_message_new sd_bus *bus sd_bus_message **m uint8_t type sd_bus_message *sd_bus_message_ref sd_bus_message *m sd_bus_message *sd_bus_message_unref sd_bus_message *m void sd_bus_message_unrefp sd_bus_message **mp sd_bus *sd_bus_message_get_bus sd_bus_message *m sd_bus_message_new() creates a new bus message object attached to the bus bus and returns it in the output parameter m. This object is reference-counted, and will be destroyed when all references are gone. Initially, the caller of this function owns the sole reference to the message object. Note that the message object holds a reference to the bus object, so the bus object will not be destroyed as long as the message exists. Note: this is a low-level call. In most cases functions like sd_bus_message_new_method_call3, sd_bus_message_new_method_error3, sd_bus_message_new_method_return3, and sd_bus_message_new_signal3 that create a message of a certain type and initialize various fields are easier to use. The type parameter specifies the type of the message. It must be one of SD_BUS_MESSAGE_METHOD_CALL — a method call, SD_BUS_MESSAGE_METHOD_RETURN — a method call reply, SD_BUS_MESSAGE_METHOD_ERROR — an error reply to a method call, SD_BUS_MESSAGE_SIGNAL — a broadcast message with no reply. The flag to allow interactive authorization is initialized based on the current value set in the bus object, see sd_bus_set_allow_interactive_authorization3. This may be changed using sd_bus_message_set_allow_interactive_authorization3. sd_bus_message_ref() increases the internal reference counter of m by one. sd_bus_message_unref() decreases the internal reference counter of m by one. Once the reference count has dropped to zero, message object is destroyed and cannot be used anymore, so further calls to sd_bus_message_ref() or sd_bus_message_unref() are illegal. sd_bus_message_unrefp() is similar to sd_bus_message_unref() but takes a pointer to a pointer to an sd_bus_message object. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute. See sd_bus_new3 for an example how to use the cleanup attribute. sd_bus_message_ref() and sd_bus_message_unref() execute no operation if the passed in bus message object address is NULL. sd_bus_message_unrefp() will first dereference its argument, which must not be NULL, and will execute no operation if that is NULL. sd_bus_message_get_bus() returns the bus object that message m is attached to. On success, sd_bus_message_new() returns 0 or a positive integer. On failure, it returns a negative errno-style error code. sd_bus_message_ref() always returns the argument. sd_bus_message_unref() always returns NULL. sd_bus_message_get_bus() always returns the bus object. Returned errors may indicate the following problems: -EINVAL Specified type is invalid. -ENOTCONN The bus parameter bus is NULL or the bus is not connected. -ENOMEM Memory allocation failed. sd_bus_message_new(), sd_bus_message_ref(), sd_bus_message_unref(), sd_bus_message_unrefp(), and sd_bus_message_get_bus() were added in version 240. systemd1 sd-bus3 sd_bus_new3 sd_bus_message_new_method_call3 sd_bus_message_new_method_error3 sd_bus_message_new_method_return3 sd_bus_message_new_signal3