FIFO

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>

#define FIFO_CHANNEL "/tmp/fifo.channel"

int main(int argc,char* argv[])
{
 int fd;
 int pid;
 char r_msg[BUFSIZ];
 char* s_msg="send message to other process";
 
 if(argc!=2){
  printf("Usage: %s opt(read-2/write-1)\n",argv[0]);
  return 1;
 }

 //write the message to the FIFO
 if(atoi(argv[1])==1){
  //FIFO 有一个路径与其关联，不能打开即用于写又读，半双工模式
  if(mkfifo(FIFO_CHANNEL,0777)==-1){
   perror("cannot create FIFO channel");
   return 1;
  }
  
  fd=open(FIFO_CHANNEL,O_WRONLY);
  if(fd==-1){
   perror("cannot open the FIFO");
   return 1;
  }
 //总是向管道尾部写数据
  if(write(fd,s_msg,strlen(s_msg))==-1){
   perror("process cannot write data to FIFO");
   return 1;
  }else
   printf("Send message: %s\n",s_msg);
 }

 //receive the message from the FIFO
 if(atoi(argv[1])==2){
  fd=open(FIFO_CHANNEL,O_RDONLY);
                if(fd==-1){
                        perror("cannot open the FIFO");
                        return 1;
                }
  //总是在管道头部读数据
  if(read(fd,r_msg,BUFSIZ)==-1){
   perror("process cannot read data from FIFO");
   return 1;
  }else
   printf("Receive message from FIFO: %s\n",r_msg);
 }

 return 0;
}