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) ; |
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).
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.
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.