sd_bus_message_new_method_call

systemd
sd_bus_message_new_method_call 3
sd_bus_message_new_method_call sd_bus_message_new_method_return Create a method call message

    #include <systemd/sd-bus.h>

int `sd_bus_message_new_method_call` sd_bus *bus sd_bus_message **m const char *destination const char *path const char *interface const char *member int `sd_bus_message_new_method_return` sd_bus_message *call sd_bus_message **m

## Description

The `sd_bus_message_new_method_call()` function creates a new bus message object that encapsulates a D-Bus method call, and returns it in the m output parameter. The call will be made on the destination destination, path path, on the interface interface, member member.

Briefly, the destination is a dot-separated name that identifies a service connected to the bus. The path is a slash-separated identifier of an object within the destination that resembles a file system path. The meaning of this path is defined by the destination. The interface is a dot-separated name that resembles a Java interface name that identifies a group of methods and signals supported by the object identified by path. Methods and signals are collectively called members and are identified by a simple name composed of ASCII letters, numbers, and underscores. See the D-Bus Tutorial for an in-depth explanation.

The destination parameter may be `NULL`. The interface parameter may be `NULL`, if the destination has only a single member with the given name and there is no ambiguity if the interface name is omitted.

Note that this is a low level interface. See sd_bus_call_method 3 for a more convenient way of calling D-Bus methods.

The `sd_bus_message_new_method_return()` function creates a new bus message object that is a reply to the method call call and returns it in the m output parameter. The call parameter must be a method call message. The sender of call is used as the destination.

## Return Value

On success, these functions return a non-negative integer. On failure, they return a negative errno-style error code.

### Errors

Returned errors may indicate the following problems:

`-EINVAL`

  The output parameter m is `NULL`.

  The destination parameter is non-null and is not a valid D-Bus service name (`org.somewhere.Something`), the path parameter is not a valid D-Bus path (`/an/object/path`), the interface parameter is non-null and is not a valid D-Bus interface name (`an.interface.name`), or the member parameter is not a valid D-Bus member (`Name`).

  The call parameter is not a method call object.

`-ENOTCONN`

  The bus parameter bus is `NULL` or the bus is not connected.

`-ENOMEM`

  Memory allocation failed.

`-EPERM`

  The call parameter is not sealed.

`-EOPNOTSUPP`

  The call message does not have a cookie.

## Examples

Make a call to a D-Bus method that takes a single parameter

This defines a minimally useful program that will open a connection to the bus, create a message object, send it, wait for the reply, and finally extract and print the answer. It does error handling and proper memory management.

## See Also

systemd 1, sd-bus 3, sd_bus_call 3, sd_bus_call_method 3, sd_bus_path_encode 3