write_shm.c

在linux下利用消息队列实现简单的聊天程序

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <signal.h>

#define SIZE 128

void my_handler(int signo)
{
}  

int main()
{
   key_t shmkey;
   int shmid;
   pid_t pid;
   char *head;   


   shmkey = ftok(".", 'a');
   shmid = shmget(shmkey, SIZE, IPC_CREAT|0666);
   head = shmat(shmid, 0, 0);

   signal(SIGUSR1,my_handler);
   while ( 1 )
   {
      if ( *((int *)head) == 0 )
      {
         usleep(500);
      }
      else
      {
         pid = *((int *)head);
         break;
      }
   }

   *((int *)head) = getpid();
   while ( 1 )
   {
      printf("send message: ");
      fgets(head+4, SIZE-4, stdin);
      kill(pid, SIGUSR1);
      pause();
   }

   return 0;
}