sig3.c

这个资料非常不错

/**********
 *sig3.c * 
 **********/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <signal.h>
#include <pwd.h>
#include <unistd.h>
#include <errno.h>

#define  MAIL_DIR   "/var/spool/mail/"

                
#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);  
}