Linux--管道

2019-11-06 07:23:29

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1. 无名管道，只适用于有亲缘关系的进程之间通信

#include <stdio.h>#include <fcntl.h>              /* Obtain O_* constant definitions */#include <unistd.h>#include <string.h>#include <stdlib.h>#define MAX_PATH 255/*	server: 接受客户端发送过来的下载文件请求，如果文件存在，则直接把数据发送给客户端	如果文件不存在，则返回出错信息给客户端*/void server(int fdCtrl, int fdData){	char fileName[MAX_PATH] = {0};	ssize_t size = 0;	size = read(fdCtrl, fileName, sizeof(fileName));	if (size == 0)	{		PRintf("end of file read/n");		return;	}		int fd;		if ((fd = open(fileName, O_RDONLY)) < 0)	{		write(fdData, "no such file/n", strlen("no such file/n"));	}	else	{		char line[1024] = {0};		while((size = read(fd, line, sizeof(line))) > 0)		{			write(fdData, line, strlen(line));			memset(line, 0x0, sizeof(line));		}		close(fd);	}}/*	client: 从标准输入键入一个文件名，然后等待服务器那端把数据传输过来*/void client(int fdCtrl, int fdData){	char fileName[MAX_PATH] = {0};		printf("please input a file:");	fgets(fileName, sizeof(fileName), stdin);		if (fileName[strlen(fileName) - 1] == '/n')	{		fileName[strlen(fileName) - 1] = 0;	}		write(fdCtrl, fileName, strlen(fileName));	//close(fdCtrl);		ssize_t size = 0;	char line[1024] = {0};	while((size = read(fdData, line, sizeof(line))) > 0)	{		write(STDOUT_FILENO, line, size);		memset(line, 0x0, sizeof(line));	}	if (size == 0)	{		printf("transfer over!!!/n");	}}int main(int argc, char **argv){	int fdCtrl[2];	int fdData[2];	pid_t pid;		//控制管道	if (pipe(fdCtrl) < 0)	{		perror("pipe");		return -1;	}		//文件管道	if (pipe(fdData) < 0)	{		perror("pipe");		return -1;	}		if ((pid = fork()) < 0)	{		perror("fork");		return -1;	}	else if (pid == 0) //child -- server	{		close(fdCtrl[1]);		close(fdData[0]);				server(fdCtrl[0], fdData[1]);		close(fdCtrl[0]);		close(fdData[1]);		exit(0);	}	else //parent -- client	{		close(fdCtrl[0]);		close(fdData[1]);				client(fdCtrl[1], fdData[0]);				waitpid(pid, NULL, 0);		close(fdCtrl[1]);		close(fdData[0]);		exit(0);	}	return 0;}
2. 有名管道，适用于有亲缘和非亲缘关系的进程，下面例子是亲缘关系间使用
#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <sys/types.h>#include <sys/stat.h>#include <string.h>#include <fcntl.h>#include <errno.h>#define FIFO1 "/tmp/control_fifo"#define FIFO2 "/tmp/data_fifo"#define FILE_MODE (S_IRUSR |S_IWUSR | S_IRGRP | S_IROTH)#define ERROR_MSG "cannot find this file/n"#define MAX_PATH 255/*	server: get the file name, then write the data to client, if the file not exists, then	write error info to client*/void server(int readfd, int writefd){	char fileName[MAX_PATH] = {0};	read(readfd, fileName, sizeof(fileName));		int fd = open(fileName, O_RDONLY);	if (fd < 0)	{		write(writefd, ERROR_MSG, strlen(ERROR_MSG));		return ;	}	else	{		ssize_t size = 0;		char line[1024] = {0};		while((size = read(fd, line, sizeof(line))) > 0)		{			write(writefd, line, size);		}	}}/*	client: input the file name, transfer to server, then wait to read data*/void client(int writefd, int readfd){	char fileName[MAX_PATH] = {0};	printf("please input a file: ");	scanf("%s", fileName);		write(writefd, fileName, strlen(fileName));		ssize_t size = 0;	char line[1024] = {0};	while((size = read(readfd, line, sizeof(line))) > 0 )	{		write(STDOUT_FILENO, line, size);	}		if (size == 0)	{		write(STDOUT_FILENO, "transfer over!!!/n", 18);	}}int main(int argc, char *argv[]){	pid_t pid;	int readfd, writefd;		if (mkfifo(FIFO1, FILE_MODE) < 0 && errno != EEXIST)	{		perror("mkfifo");		return -1;	}		if (mkfifo(FIFO2, FILE_MODE) < 0 && errno != EEXIST)	{		perror("mkfifo");		return -1;	}		if ((pid = fork()) == 0)	{		readfd = open(FIFO1, O_RDONLY);		writefd = open(FIFO2, O_WRONLY);		server(readfd, writefd);				close(readfd);		close(writefd);	}	else if(pid > 0)	{		writefd = open(FIFO1, O_WRONLY);		readfd = open(FIFO2, O_RDONLY);		client(writefd, readfd);				waitpid(pid, NULL, 0);		close(writefd);		close(readfd);				unlink(FIFO1);		unlink(FIFO2);	}	else	{		printf("fork error/n");		return -1;	}	//int mkfifo(const char *pathname, mode_t mode);	return 0;}3. 非亲缘关系进程间通信
fifo_read.c
#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <sys/types.h>#include <sys/stat.h>#include <string.h>#include <fcntl.h>#include <errno.h>#define FIFO1 "/tmp/control_fifo"#define FILE_MODE (S_IRUSR |S_IWUSR | S_IRGRP | S_IROTH)#define ERROR_MSG "cannot find this file/n"#define MAX_PATH 255int main(int argc, char *argv[]){	int fd;		if (mkfifo(FIFO1, FILE_MODE) < 0 && errno != EEXIST)	{		perror("mkfifo");		return -1;	}		fd = open(FIFO1, O_RDONLY);	if (fd < 0)	{		perror("open");		return -1;	}		ssize_t size = 0;	char line[1024] = {0};	if ((size = read(fd, line, sizeof(line))) > 0)	{		write(STDOUT_FILENO, line, size);	}		return 0;}fifo_write.c
#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <sys/types.h>#include <sys/stat.h>#include <string.h>#include <fcntl.h>#include <errno.h>#define FIFO1 "/tmp/control_fifo"#define FILE_MODE (S_IRUSR |S_IWUSR | S_IRGRP | S_IROTH)#define ERROR_MSG "cannot find this file/n"#define MAX_PATH 255int main(int argc, char *argv[]){	int fd;		if (mkfifo(FIFO1, FILE_MODE) < 0 && errno != EEXIST)	{		perror("mkfifo");		return -1;	}		fd = open(FIFO1, O_WRONLY);	if (fd < 0)	{		perror("open");		return -1;	}		ssize_t size = 0;	char line[1024] = {"gzhang love zhengcx/n"};	if ((size = write(fd, line, strlen(line))) > 0)	{		printf("transfer over!/n");	}		return 0;}