NAME

       sd_bus_wait - Wait for I/O on a bus connection

SYNOPSIS

       #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_usec 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.

NOTES

       Functions described here are available as a shared library, which can be compiled against
       and linked to with the libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be not multi-thread-safe.
       This means that the code calling the functions described here must not call setenv(3) from
       a parallel thread. It is recommended to only do calls to setenv() from an early phase of
       the program when no other threads have been started.

HISTORY

       sd_bus_wait() was added in version 240.

SEE ALSO

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