Linux---Use of pipe communication

Operation of anonymous pipes

Communication can only be carried out between related processes.
int pipe(int pipefd[2])

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>

int main()
{
    
    
	int pipefd[2] = {
    
    -1};
	int ret = pipe(pipefd);
	if(ret < 0)
	{
    
    
		perror("pipe error");
		return -1;
	}

	pid_t pid = fork();
	if(pid == 0)
	{
    
    
		char buf[1024];
		read(pipefd[0],buf,1023);
	}
	else if(pid > 0)
	{
    
    
		char *str = "hello";
		write(pipefd[1],biff,str);
	}
	
	return 0;
}

Operation of named pipes:

Supports access between different processes in the same host.
int mkfifo(char* name, mode_t mode)//Pipe name and permissions.

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<sys/stat.h> //命名管道
#include<errno.h>	//错误处理
#include<fcntl.h>	//文件操作

int main()
{
    
    
	umask(0); //设置权限信息
	//mkfifo(命名管道名称，管道操作权限)
	int ret = mkfifo("./test_fifo",664);
	if(ret < 0 && error != EEXIST) //创建失败或者已经存在
	{
    
    
		perror("mkfifo error");
		return -1;
	}
	int fd = open("./test.fifo",O_RDONLY); //以只读的方式打开文件
	if(fd < 0)
	{
    
    
		perror("open fifo error");
		return -1;
	}
	
	return 0;
}

note

文件以只读的方式打开，则会被阻塞，直到文件用写的方式进行打开。
文件以只写的方式打开，则会被阻塞，直到文件用读的方式打开。

Read and write characteristics of the pipeline:

• The pipeline is half-duplex communication, and the direction can be selected for data transmission.
• If there is no data in the pipeline, read will block, and if the data in the pipeline is full, write will block.
• If an exception occurs on the write end of the pipeline, the read end will return 0 after reading the data in the pipeline and it is not blocked.
• If the read end of the pipe is closed, an error is reported for the write segment.
• The life cycle of the pipeline varies with the process. When all processes operating the pipeline are exited, the pipeline is released.
• The pipe provides byte stream transmission service and does not read the same data.
• The pipeline comes with synchronization and mutual exclusion.

The pipeline comes with synchronization and mutual exclusion

Synchronization: Realize the timing rationality of access to critical resources through conditional judgment. Reflected in the pipeline, the read and write characteristics of the pipeline are
mutually exclusive: the security of access to critical resources is achieved through unique access. Pipeline read and write operations are guaranteed atomicity in PIPE_BUF.