Question

I want to handle SIGUSR1 signal so I do everything what it needs and it´s working. But in my program I am waiting at recvfrom and when I handle signal and return then to recvfrom I got -1 from this function. Is it possible to return back to waiting at this function?

Answer 1

Your system call is being interrupted by the signal. Unless you are consistently setting up signal handlers using sigaction with the SA_RESTART flag, it is a good idea to retry system calls using a loop such as:

while ((size = recvfrom(...)) == -1 && errno == EINTR)
  ;