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Examples&Exercises:

  1. Using a Signal Handler; completed. http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/sigusr1works.csigusr1works.c
    #include <signal.h>
    #include <stdio.h>
    #include <string.h>
    #include <sys/types.h>
    #include <unistd.h>
    #include <time.h>
    sig_atomic_t sigusr1_count = 0;
    void handler (int signal_number)
    {
      time_t cur_time;
      char *chartime;
      int stat;
      cur_time = time(NULL);
      if ( cur_time == -1 ) {
        perror( "Error getting time");
        exit(1);
      }
      chartime = ctime(&cur_time);
      printf( "SIGUSR1 received on %s", ctime(&cur_time) );
      ++sigusr1_count;
      printf ("IN HANDLER: SIGUSR1 was raised %d times\n", sigusr1_count);
    }
    int main ()
    {
      int i,j;
      pid_t child[5];
      struct sigaction sa;
      memset (&sa, 0, sizeof (sa));
      sa.sa_handler = &handler;
      sigaction (SIGUSR1, &sa, NULL);
      child[1]=fork();
      if (child[1] !=0)
        printf("I am the parent  \n");
      else
        {
          sleep(5);
          int pid = getpid();
          printf("\n I am the first child with pid=%d   \n",pid);
          kill(pid,SIGUSR1);
          child[2]=fork();
          if (child[2] !=0)
            printf("I am the parent of the second child \n");
          else
            {
              sleep(5);
              int pid = getpid();
              printf("\n I am the second child with pid=%d   \n",pid);
              kill(getpid(),SIGUSR1);
            }
        }
      printf ("IN MAIN: SIGUSR1 was raised %d times\n", sigusr1_count);
      printf ("******************************************");
      return 0;
    }
    
  2. Cleaning Up Children Asynchronously; completed. http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/cleaningworks.ccleaningworks.c
    #include <signal.h>
    #include <string.h>
    #include <sys/types.h>
    #include <sys/wait.h>
    sig_atomic_t child_exit_status;
    void clean_up_child_process (int signal_number)
    {
      /* Clean up the child process.  */
      int status;
      printf("I am in clenup function now and cleaning this child \n");
      wait (&status);
      /* Store its exit status in a global variable.  */
      child_exit_status = status;
      printf("child_exit_status=%d with pid=%d \n", child_exit_status,
              getpid());
      printf("bla bla bla \n");
      printf("-------------------------------------------------------\n");
    }
    int main ()
    {
      pid_t child_pid,child2;
      /* Handle SIGCHLD by calling clean_up_child_process.  */
      struct sigaction sigchld_action;
      memset (&sigchld_action, 0, sizeof (sigchld_action));
      sigchld_action.sa_handler = &clean_up_child_process;
      sigaction (SIGCHLD, &sigchld_action, NULL);
      printf("Before child_exit_status=%d with pid=%d \n",
              child_exit_status, getpid());
      printf("-------------------------------------------------------\n");
      child_pid=fork();
      if (child_pid!=0)
        {
          sleep(5);
          printf("I am the parent  \n");
        }
      else
        {
          child2=fork();
          if(child2!=0)
            {
              sleep(4);
              printf("I am the first child with pid=%d and
              child_exit_status= %d  \n",getpid(),child_exit_status);
            }
          else
            {
              sleep(3);
              printf("I am the second child with pid=%d and 
              child_exit_status=%d  \n",getpid(),child_exit_status);
            }
        }
      return 0;
    }
    
  3. Catching signals; http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/sig_talk.csig_talk.c.
  4. Thread Creation; http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/thread-create.cthread-create.c
    #include <pthread.h>
    #include <stdio.h>
    /* Prints x's to stderr.  The parameter is unused.  Does not return.  */
    void* print_xs (void* unused)
    {
      while (1) 
        fputc ('x', stderr);
      return NULL;
    }
    /* The main program.  */
    int main ()
    {
      pthread_t thread_id;
      /* Create a new thread.  The new thread will run the print_xs
         function.  */
      pthread_create (&thread_id, NULL, &print_xs, NULL);
      /* Print o's continuously to stderr.  */
      while (1) 
        fputc ('o', stderr);
      return 0;
    }
    
  5. Passing Data to Threads; http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/thread-create2.cthread-create2.c
  6. Thread Return Values; http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/primes.cprimes.c.
  7. Thread Attributes; http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/detached.cdetached.c.
  8. Thread-Specific Data; http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/tsd.ctsd.c

next up previous contents
Next: Semaphores for Threads Up: SYSTEMS PROGRAMMING LABORATORY V Previous: SYSTEMS PROGRAMMING LABORATORY V   Contents
Cem Ozdogan 2007-05-16