Linux 进程间通信 (IPC) //管道

//消息队列

1

//信号量

4

//管道

#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main()
{
int pipe_fd[2];
pid_t pid;
char buf_r[100];
char* p_wbuf;
int r_num;

memset(buf_r,0,sizeof(buf_r));

/*创建管道*/
if(pipe(pipe_fd)<0)
{
printf("pipe create error\n");
return -1;
}

/*创建子进程*/
if((pid=fork())==0) //子进程执行序列
{
printf("\n");
close(pipe_fd[1]);//子进程先关闭了管道的写端
sleep(2); /*让父进程先运行，这样父进程先写子进程才有内容读*/
if((r_num=read(pipe_fd[0],buf_r,100))>0)
{
printf("%d numbers read from the pipe is %s\n",r_num,buf_r);
}
close(pipe_fd[0]);
exit(0);
}
else if(pid>0) //父进程执行序列
{
close(pipe_fd[0]); //父进程先关闭了管道的读端
if(write(pipe_fd[1],"Hello",5)!=-1)
printf("parent write1 Hello!\n");
if(write(pipe_fd[1]," Pipe",5)!=-1)
printf("parent write2 Pipe!\n");
close(pipe_fd[1]);
waitpid(pid,NULL,0); /*等待子进程结束*/
exit(0);
}
return 0;
}


#include <sys/types.h>

#include <sys/stat.h>

#include <errno.h>

#include <fcntl.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#define FIFO "/tmp/myfifo"

int main(int argc,char** argv)

{
char buf_r[100];
int  fd;
int  nread;

printf("Preparing for reading bytes...\n");
memset(buf_r,0,sizeof(buf_r));

/* 打开管道 */
fd=open(FIFO,O_RDONLY|O_NONBLOCK,0);
if(fd==-1)
{
perror("open");
exit(1);

}
while(1)
{
memset(buf_r,0,sizeof(buf_r));

if((nread=read(fd,buf_r,100))==-1)
{
if(errno==EAGAIN)
printf("no data yet\n");
}
printf("read %s from FIFO\n",buf_r);
sleep(1);
}

    //后面三句话是不会被运行到的，但不会影响程序运行的效果当程序在上面的死循环中执行时收到信号后会马上结束运行而没有执行后面的三句话。这些会在后面的信号处理中讲到，现在不理解没有关系，这个问题留给大家学习了信号处理之后来解决。
close(fd); //关闭管道
pause(); /*暂停，等待信号*/
unlink(FIFO); //删除文件

}

#include <sys/types.h>

#include <sys/stat.h>

#include <errno.h>

#include <fcntl.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#define FIFO_SERVER "/tmp/myfifo"

int main(int argc,char** argv)

{
int fd;
char w_buf[100];
int nwrite;

    /*创建有名管道*/
if((mkfifo(FIFO_SERVER,O_CREAT|O_EXCL|O_RDWR)<0)&&(errno!=EEXIST))
printf("cannot create fifoserver\n");

/*打开管道*/
fd=open(FIFO_SERVER,O_RDWR|O_NONBLOCK,0);
if(fd==-1)
{
   perror("open");
exit(1);
}

/*入参检测*/
if(argc==1)
{
printf("Please send something\n");
exit(-1);
}
strcpy(w_buf,argv[1]);

/* 向管道写入数据 */
if((nwrite=write(fd,w_buf,100))==-1)
{
if(errno==EAGAIN)
printf("The FIFO has not been read yet.Please try later\n");
}
else 
printf("write %s to the FIFO\n",w_buf);
close(fd); //关闭管道
return 0;

}

//

fd=open(FIFO,O_RDONLY|O_NONBLOCK,0);

4

//共享内存

4

//套接字 

4