signals/signalfd_sigval.c

+/* signalfd_sigval.c
+
+   Usage: signalfd_sigval sig-num...
+
+   Demonstrate the use of signalfd() to receive signals via a file descriptor.
+
+   This program is Linux-specific. The signalfd API is supported since kernel
+   2.6.22.
+*/
 #include <sys/signalfd.h>
 #include <signal.h>
 #include "tlpi_hdr.h"
 
 int
 main(int argc, char *argv[])
 {
     sigset_t mask;
     int sfd, j;
     struct signalfd_siginfo fdsi;
     ssize_t s;
 
     if (argc < 2 || strcmp(argv[1], "--help") == 0)
         usageErr("%s sig-num...\n", argv[0]);
 
     printf("%s: PID = %ld\n", argv[0], (long) getpid());
 
     sigemptyset(&mask);
     for (j = 1; j < argc; j++)
         sigaddset(&mask, atoi(argv[j]));
 
     if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1)
         errExit("sigprocmask");
 
     sfd = signalfd(-1, &mask, 0);
     if (sfd == -1)
         errExit("signalfd");
 
     for (;;) {
         s = read(sfd, &fdsi, sizeof(struct signalfd_siginfo));
         if (s != sizeof(struct signalfd_siginfo))
             errExit("read");
 
         printf("%s: got signal %d", argv[0], fdsi.ssi_signo);
         if (fdsi.ssi_code == SI_QUEUE) {
             printf("; ssi_pid = %d; ", fdsi.ssi_pid);
             printf("ssi_int = %d", fdsi.ssi_int);
         }
         printf("\n");
     }
 }