11-6.c

《Linux应用开发技术详解》附书光盘中的例程。

 #include <stdio.h>
   #include <signal.h>
   #include <string.h>
   #include <unistdio.h>
   #include <sys/type.h>
   #include <stdlib.h>
  * Linux 的默任个人的邮箱地址是 /var/spool/mail/ */ 
  #define MAIL_DIR "/var/spool/mail/" 
  * 睡眠10秒钟 */ 
  #define SLEEP_TIME 10 
  #define MAX_FILENAME 255 
  unsigned char notifyflag=1; 
  long get_file_size(const char *filename) 
  { 
    struct stat buf; 
    if(stat(filename,&;buf)==-1) 
    { 
       if(errno==ENOENT)
         {  
               return 0; 
         }
       else
            {
                 return -1; 
             } 
       }
      return (long)buf.st_size; 
    } 
   void send_mail_notify(void) 
    { 
        fprintf(stderr,"New mail has arrived\007\n"); 
    } 
 
   void turn_on_notify(int signo) 
    { 
      notifyflag=1; 
    } 

   void turn_off_notify(int signo) 
   { 
      notifyflag=0; 
   } 

  int check_mail(const char *filename) 
  { 
      long old_mail_size,new_mail_size; 
      sigset_t blockset,emptyset; 
      sigemptyset(&;blockset); 
      sigemptyset(&;emptyset); 
      sigaddset(&;blockset,SIGUSR1); 
      sigaddset(&;blockset,SIGUSR2); 
      old_mail_size=get_file_size(filename); 
      if(old_mail_size<0)
         {
             return 1;
         } 
      if(old_mail_size>0) 
        {
           send_mail_notify(); 
        }
      sleep(SLEEP_TIME); 
 
     while(1) 
         { 
          if(sigprocmask(SIG_BLOCK,&;blockset,NULL)<0) 
             {
                  return 1; 
             }  
         while(notifyflag==0)
             {
                 sigsuspend(&;emptyset); 
                  if(sigprocmask(SIG_SETMASK,&;emptyset,NULL)<0)
                   {
                         return 1;
             } 
        new_mail_size=get_file_size(filename); 
        if(new_mail_size>old_mail_size)
            {
              send_mail_notify; 
            }
        old_mail_size=new_mail_size; 
        sleep(SLEEP_TIME); 
      } 
   } 
 int main(void) 
   { 
      char mailfile[MAX_FILENAME]; 
      struct sigaction newact; 
      struct passwd *pw; 

      if((pw=getpwuid(getuid()))==NULL) 
        { 
           fprintf(stderr,"Get Login Name Error:%s\n\a",strerror(errno)); 
            exit(1); 
         } 
     strcpy(mailfile,MAIL_DIR); 
    strcat(mailfile,pw->pw_name); 
     newact.sa_handler=turn_on_notify; 
     newact.sa_flags=0; 
     sigemptyset(&;newact.sa_mask); 
     sigaddset(&;newact.sa_mask,SIGUSR1); 
     sigaddset(&;newact.sa_mask,SIGUSR2); 
    if(sigaction(SIGUSR1,&;newact,NULL)<0) 
    fprintf(stderr,"Turn On Error:%s\n\a",strerror(errno)); 
     newact.sa_handler=turn_off_notify; 
     if(sigaction(SIGUSR1,&;newact,NULL)<0) 
     fprintf(stderr,"Turn Off Error:%s\n\a",strerror(errno)); 
     check_mail(mailfile); 
     exit(0); 
  }