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)