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

       These APIs are implemented as a shared library, which can be compiled and linked to with the
       libsystemd pkg-config(1) file.

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)