sd_bus_message_new_signal

systemd
sd_bus_message_new_signal 3
sd_bus_message_new_signal Create a signal message

    #include <systemd/sd-bus.h>

int sd_bus_message_new_signal sd_bus *bus sd_bus_message **m const char *path const char *interface const char *member

## Description

The `sd_bus_message_new_signal()` function creates a new bus message object that encapsulates a D-Bus signal, and returns it in the m output parameter. The signal will be sent to path path, on the interface interface, member member. When this message is sent, no reply is expected. See sd_bus_message_new_call 1 for a short description of the meaning of the path, interface, and member parameters.

## Return Value

This function returns 0 if the message object was successfully created, and a negative errno-style error code otherwise.

### Errors

Returned errors may indicate the following problems:

`-EINVAL`

  The output parameter m is `NULL`.

  The path parameter is not a valid D-Bus path (`/an/object/path`), the interface parameter is not a valid D-Bus interface name (`an.interface.name`), or the member parameter is not a valid D-Bus member (`Name`).

`-ENOTCONN`

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

`-ENOMEM`

  Memory allocation failed.

## Examples

Send a simple signal

This function in systemd sources is used to emit the `UnitFilesChanged` signal when the unit files have been changed.

## See Also

systemd 1, sd-bus 3