sd_bus_message_get

Name

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

Synopsis

#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.

Notes¶

Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file.

The code described here uses getenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call setenv(3) from a parallel thread. It is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started.

History¶

sd_bus_message_get_type(), sd_bus_message_is_signal(), sd_bus_message_is_method_call(), and sd_bus_message_is_method_error() were added in version 240.

sd_bus_message_get_error(), sd_bus_message_get_errno(), and sd_bus_message_get_creds() were added in version 246.