systemd sd_bus_message_get_type 3 sd_bus_message_get_type sd_bus_message_get_error sd_bus_message_get_errno sd_bus_message_get_creds sd_bus_message_is_signal sd_bus_message_is_method_call sd_bus_message_is_method_error Query bus message addressing/credentials metadata #include <systemd/sd-bus.h> int sd_bus_message_get_type sd_bus_message *m uint8_t *type sd_bus_error* sd_bus_message_get_error sd_bus_message *m int sd_bus_message_get_errno sd_bus_message *m sd_bus_creds* sd_bus_message_get_creds sd_bus_message *m int sd_bus_message_is_signal sd_bus_message *m const char *interface const char *member int sd_bus_message_is_method_call sd_bus_message *m const char *interface const char *member int sd_bus_message_is_method_error sd_bus_message *m const char *name sd_bus_message_get_type() returns the type of a message in the output parameter type, one of SD_BUS_MESSAGE_METHOD_CALL, SD_BUS_MESSAGE_METHOD_RETURN, SD_BUS_MESSAGE_METHOD_ERROR, SD_BUS_MESSAGE_SIGNAL. This type is either specified as a parameter when the message is created using sd_bus_message_new3, or is set automatically when the message is created using sd_bus_message_new_signal3, sd_bus_message_new_method_call3, sd_bus_message_new_method_error3 and similar functions. sd_bus_message_get_error() returns the error stored in the message m, if there is any. Otherwise, it returns NULL. sd_bus_message_get_errno() returns the error stored in the message m as a positive errno-style value, if there is any. Otherwise, it returns zero. Errors are mapped to errno values according to the default and any additional registered error mappings. See sd-bus-errors3 and sd_bus_error_add_map3. sd_bus_message_get_creds() returns the message credentials attached to the message m. If no credentials are attached to the message, it returns NULL. Ownership of the credentials instance is not transferred to the caller and hence should not be freed. sd_bus_message_is_signal() checks if message m is a signal message. If interface is non-null, it also checks if the message has the same interface set. If member is non-null, it also checks if the message has the same member set. Also see sd_bus_message_new_signal3. It returns true when all checks pass. sd_bus_message_is_method_call() checks if message m is a method call message. If interface is non-null, it also checks if the message has the same interface set. If member is non-null, it also checks if the message has the same member set. Also see sd_bus_message_new_method_call3. It returns true when all checks pass. sd_bus_message_is_method_error() checks if message m is an error reply message. If name is non-null, it also checks if the message has the same error identifier set. Also see sd_bus_message_new_method_error3. It returns true when all checks pass. On success, these functions (except sd_bus_message_get_error() and sd_bus_message_get_creds()) return a non-negative integer. On failure, they return a negative errno-style error code. sd_bus_message_get_errno() always returns a non-negative integer, even on failure. Returned errors may indicate the following problems: -EINVAL The message parameter m or an output parameter is NULL. systemd1, sd-bus3, sd_bus_message_new3, sd_bus_message_set_destination3, sd-bus-errors3, sd_bus_error_add_map3