SD_BUS_WAIT(3)

  .SH "NAME" sd_bus_wait - Wait for I/O on a bus connection
  .SH "SYNOPSIS"

#include <systemd/sd-bus.h>

      .HP u int sd_bus_wait(sd_bus *bus, uint64_t timeout_usec);

  .SH "DESCRIPTION"

    .PP 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(3), 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.
    .PP 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.
    .PP 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).

  .SH "RETURN VALUE"

    .PP 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.

  .SH "ERRORS"

    .PP Returned errors may indicate the following problems:

      .PP -EINVAL

            An invalid bus object was passed.
          .RE
          .PP -ECHILD

                The bus connection was allocated in a parent process and is being reused in a child process after fork().
              .RE
              .PP -ENOTCONN

                    The bus connection has been terminated already.
                  .RE

              .SH "NOTES"

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

                .PP systemd(1), sd-bus(3), sd_bus_process(3), sd_bus_get_fd(3), sd-event(3), sd_bus_attach_event(3)