sd_bus_message_get_type

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

## Description

`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_new 3, or is set automatically when the message is created using sd_bus_message_new_signal 3, sd_bus_message_new_method_call 3, sd_bus_message_new_method_error 3 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-errors 3 and sd_bus_error_add_map 3.

`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_signal 3. 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_call 3. 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_error 3. It returns true when all checks pass.

## Return Value

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.

### Errors

Returned errors may indicate the following problems:

`-EINVAL`

  The message parameter m or an output parameter is `NULL`.

## See Also

systemd 1, sd-bus 3, sd_bus_message_new 3, sd_bus_message_set_destination 3, sd-bus-errors 3, sd_bus_error_add_map 3