sd_bus_wait

systemd
sd_bus_wait 3
sd_bus_wait Wait for I/O on a bus connection

    #include <systemd/sd-bus.h>

int `sd_bus_wait` sd_bus *bus uint64_t timeout_usec

## Description

`sd_bus_wait()` synchronously waits for I/O on the specified bus connection object. This function is supposed to be called whenever sd_bus_process 3 returns zero, indicating that no work is pending on the connection. Internally, this call invokes ppoll 2, to wait for I/O on the bus connection. If the timeout_sec parameter is specified, the call will block at most for the specified amount of time in µs. Pass `UINT64_MAX` to permit it to sleep indefinitely.

After each invocation of `sd_bus_wait()` the `sd_bus_process()` call should be invoked in order to process any now pending I/O work.

Note that `sd_bus_wait()` is suitable only for simple programs as it does not permit waiting for other I/O events. For more complex programs either connect the bus connection object to an external event loop using sd_bus_get_fd 3 or to an sd-event 3 event loop using sd_bus_attach_event 3.

## Return Value

If any I/O was seen, a positive value is returned, zero otherwise. If an error occurs, a negative `errno`-style error code is returned.

### Errors

Returned errors may indicate the following problems:

`-EINVAL`

  An invalid bus object was passed.

`-ECHILD`

  The bus connection was allocated in a parent process and is being reused in a child process after `fork()`.

`-ENOTCONN`

  The bus connection has been terminated already.

## See Also

systemd 1, sd-bus 3, sd_bus_process 3, sd_bus_get_fd 3, sd-event 3, sd_bus_attach_event 3