pgsjc/disc_SIGHUP.c

+/* disc_SIGHUP.c
+
+   This program demonstrates that when a "terminal disconnect" occurs, SIGHUP
+   is sent to all the members of the foreground process group for this terminal.
+
+   Try using the following command to run this program in an X-window, and then
+   closing the window:
+
+        exec disc_SIGHUP > sig.log 2>&1
+
+   (Since the above will replace the shell with this program, it will be the
+   controlling process for the terminal.)
+*/
 #define _GNU_SOURCE     /* Get strsignal() declaration from <string.h> */
 #include <string.h>
 #include <signal.h>
 #include "tlpi_hdr.h"
 
 static void             /* Handler for SIGHUP */
 handler(int sig)
 {
     printf("PID %ld: caught signal %2d (%s)\n", (long) getpid(),
             sig, strsignal(sig));
                         /* UNSAFE (see Section 21.1.2) */
 }
 
 int
 main(int argc, char *argv[])
 {
     pid_t parentPid, childPid;
     int j;
     struct sigaction sa;
 
     if (argc < 2 || strcmp(argv[1], "--help") == 0)
         usageErr("%s {d|s}... [ > sig.log 2>&1 ]\n", argv[0]);
 
     setbuf(stdout, NULL);               /* Make stdout unbuffered */
 
     parentPid = getpid();
     printf("PID of parent process is:       %ld\n", (long) parentPid);
     printf("Foreground process group ID is: %ld\n",
             (long) tcgetpgrp(STDIN_FILENO));
 
     for (j = 1; j < argc; j++) {        /* Create child processes */
         childPid = fork();
         if (childPid == -1)
             errExit("fork");
 
         if (childPid == 0) {            /* If child... */
             if (argv[j][0] == 'd')      /* 'd' --> to different pgrp */
                 if (setpgid(0, 0) == -1)
                     errExit("setpgid");
 
             sigemptyset(&sa.sa_mask);
             sa.sa_flags = 0;
             sa.sa_handler = handler;
             if (sigaction(SIGHUP, &sa, NULL) == -1)
                 errExit("sigaction");
             break;                      /* Child exits loop */
         }
     }
 
     /* All processes fall through to here */
 
     alarm(60);      /* Ensure each process eventually terminates */
 
     printf("PID=%ld PGID=%ld\n", (long) getpid(), (long) getpgrp());
     for (;;)
         pause();        /* Wait for signals */
 }