Example

     The following example shows how to generate and use a signal
     mask that blocks only the SIGINT signal from delivery:

              #include <signal.h>
              int return_value;
              sigset_t newset;
                . . .
              sigemptyset(&newset);
              sigaddset(&newset, SIGINT);
              return_value = sigprocmask (SIG_SETMASK, &newset, NULL);