Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Mail Systems
Eclipse Documentation

How To Guides
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Problem Solutions
Privacy Policy




24.7.4 Blocking to Test for Delivery of a Signal

Now for a simple example. Suppose you establish a handler for SIGALRM signals that sets a flag whenever a signal arrives, and your main program checks this flag from time to time and then resets it. You can prevent additional SIGALRM signals from arriving in the meantime by wrapping the critical part of the code with calls to sigprocmask, like this:

     /* This variable is set by the SIGALRM signal handler. */
     volatile sig_atomic_t flag = 0;
     main (void)
       sigset_t block_alarm;
       /* Initialize the signal mask. */
       sigemptyset (&block_alarm);
       sigaddset (&block_alarm, SIGALRM);
       while (1)
           /* Check if a signal has arrived; if so, reset the flag. */
           sigprocmask (SIG_BLOCK, &block_alarm, NULL);
           if (flag)
               flag = 0;
           sigprocmask (SIG_UNBLOCK, &block_alarm, NULL);

  Published under the terms of the GNU General Public License Design by Interspire