进程间通讯(三).signal

/* Set the handler for the signal SIG to HANDLER, returning the old
   handler, or SIG_ERR on error.
   By default `signal' has the BSD semantic.  */
__BEGIN_NAMESPACE_STD
#ifdef __USE_BSD
extern __sighandler_t signal (int __sig, __sighandler_t __handler)
     __THROW;
#else

emacs@ubuntu:/usr/include$ kill -l 
 1) SIGHUP	 2) SIGINT	 3) SIGQUIT	 4) SIGILL	 5) SIGTRAP
 6) SIGABRT	 7) SIGBUS	 8) SIGFPE	 9) SIGKILL	10) SIGUSR1
11) SIGSEGV	12) SIGUSR2	13) SIGPIPE	14) SIGALRM	15) SIGTERM
16) SIGSTKFLT	17) SIGCHLD	18) SIGCONT	19) SIGSTOP	20) SIGTSTP
21) SIGTTIN	22) SIGTTOU	23) SIGURG	24) SIGXCPU	25) SIGXFSZ
26) SIGVTALRM	27) SIGPROF	28) SIGWINCH	29) SIGIO	30) SIGPWR
31) SIGSYS	34) SIGRTMIN	35) SIGRTMIN+1	36) SIGRTMIN+2	37) SIGRTMIN+3
38) SIGRTMIN+4	39) SIGRTMIN+5	40) SIGRTMIN+6	41) SIGRTMIN+7	42) SIGRTMIN+8
43) SIGRTMIN+9	44) SIGRTMIN+10	45) SIGRTMIN+11	46) SIGRTMIN+12	47) SIGRTMIN+13
48) SIGRTMIN+14	49) SIGRTMIN+15	50) SIGRTMAX-14	51) SIGRTMAX-13	52) SIGRTMAX-12
53) SIGRTMAX-11	54) SIGRTMAX-10	55) SIGRTMAX-9	56) SIGRTMAX-8	57) SIGRTMAX-7
58) SIGRTMAX-6	59) SIGRTMAX-5	60) SIGRTMAX-4	61) SIGRTMAX-3	62) SIGRTMAX-2
63) SIGRTMAX-1	64) SIGRTMAX	
emacs@ubuntu:/usr/include$

emacs@ubuntu:/usr/include$ grep SIGINT *   -r 
asm/signal.h:#define SIGINT		 2
asm-generic/signal.h:#define SIGINT		 2
bits/signum.h:#define	SIGINT		2	/* Interrupt (ANSI).  */
linux/reboot.h: * CAD_OFF     Ctrl-Alt-Del sequence sends SIGINT to init task.
python2.6/pyconfig.h:#define HAVE_SIGINTERRUPT 1
rpcsvc/rex.x:const SIGINT = 2;	/* interrupt */
rpcsvc/rex.h:#define SIGINT 2
emacs@ubuntu:/usr/include$

#include <stdio.h>
#include <signal.h> //signal，kill 函数的原型声明在里面
#include <unistd.h>

void trigger(int signum)  //定义一个触发函数，在收到信号后被调用
{
  printf("T:A,I have received your signal , now I will kill you!, the signal is %d\n",signum); //打印一句话，并且将收到的信号打印出来
}


int main()
{
  pid_t ret=0;
  int res=-1; // 初始化变量
  printf("X:befor fork\n"); 
  ret=fork(); //分裂出新进程
  printf("X:after fork:%d\n",ret);
  if(0 == ret) //A ，也就是子进程
  {
    int sig=40;
    pid_t pid=getpid(),ppid=getppid(); //获取自己的和父亲的进程号
    sleep(3); //沉睡3秒
    printf("A:this is child, my pid is %d , I am ready to sent sig %d to process which pid is %d\n",pid,sig,ppid); //打印出当前的状态
    if(0 == kill(ppid,sig)) //给父进程发送指定信号，在这里kill并不是杀死的意义，而是发送信号的意义
    {
      printf("A:sent %d signal to %d\n",sig,ppid);
    }
    else  //进行容错处理
    {
      perror("A:kill");
      return res;
    }
  }
  else if(0 < ret) //B ，也就是父进程
  {
    pid_t pid=getpid(),cpid=ret; //获取自己的和子进程的进程号
    int sig=9;
    printf("B:this is father, pid is %d, cpid is %d\n",pid,cpid); //将当前状态进行显示
    signal(40,trigger); //收到40号信号后，执行trigger函数
    pause(); //在收到信号之前，一直处于阻塞状态
    if(0 == kill(cpid,sig)) //给子进程发送信号
    {
      printf("B:sent %d signal to %d\n",sig,cpid);
    }
    else  
    {
      perror("B:kill");
    }
  }
  else //对于fork失败的容错处理
  {
    perror("X:fork\n");
    return res;
  }
  res=0;
  return res;  
}

emacs@ubuntu:~/c$ alias gtc
alias gtc='gcc -Wall -g -o'
emacs@ubuntu:~/c$ gtc signal.x signal.c
emacs@ubuntu:~/c$ ./signal.x 
X:befor fork
X:after fork:17082
B:this is father, pid is 17081, cpid is 17082
X:after fork:0
A:this is child, my pid is 17082 , I am ready to sent sig 40 to process which pid is 17081
A:sent 40 signal to 17081
T:A,I have received your signal , now I will kill you!, the signal is 40
B:sent 9 signal to 17082
emacs@ubuntu:~/c$

/* Send signal SIG to process number PID.  If PID is zero,
   send SIG to all processes in the current process's process group.
   If PID is < -1, send SIG to all processes in process group - PID.  */
#ifdef __USE_POSIX
extern int kill (__pid_t __pid, int __sig) __THROW;
#endif /* Use POSIX.  */

/* Suspend the process until a signal arrives.
   This always returns -1 and sets `errno' to EINTR.

   This function is a cancellation point and therefore not marked with
   __THROW.  */
extern int pause (void);