unix网络编程卷2：管道和FIFO

管道和FIFO

1. 管道（Pipe）：管道可用于具有亲缘关系进程间的通信，允许一个进程和另一个与它有共同祖先的进程之间进行通信。
2. 命名管道（named pipe）：命名管道克服了管道没有名字的限制，因此，除具有管道所具有的功能外，它还允许无亲缘关系进程间的通信。命名管道在文件系统中有对应的文件名。命名管道通过命令mkfifo或系统调用mkfifo来创建。

#include 
int pipe（int fd[2]）

该函数返回两个文件描述符 fd[[0]和fdp[1],前者用于读，后者用于写。

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

void client(int readfd, int writefd);
void server(int readfd, int writefd);

int main(int argc,char **argv)
{
    int pipe1[2], pipe2[2];
    int childpid;

    pipe(pipe1);
    pipe(pipe2);

    if( (childpid = fork()) == 0)  //child
    {
        close(pipe1[1]);
        close(pipe2[0]);

        server(pipe1[0],pipe2[1]);
        exit(0);
    }

    close(pipe1[0]);
    close(pipe2[1]);

    client(pipe2[0],pipe1[1]);

    waitpid(childpid, NULL, 0);
    exit(0);
}

void server(int readfd, int writefd)
{
    int fd;
    size_t n;
    char buff[4097];

    if( (n = read(readfd, buff, 4096)) == 0)
    {
        std::cout<< "read file error " << std::endl;
        return;
    }

    buff[n] = '\0';
    std::cout << "the server get filename from client:" << buff << std::endl;

    if( (fd = open(buff, O_RDONLY)) < 0)
    {
        std::cout << "the file file can't open file" << std::endl;  
        write(writefd, buff , n);
    }
    else
    {
        while( (n = read(fd, buff, 4096)) > 0)
        {
            std::cout << "the server read file:" << buff;
            write(writefd, buff , n);
        }

        close(fd);
    }
}

void client(int readfd, int writefd)
{
    size_t len;
    size_t n;

    char buff[4097];
    std::cout<< "pls input filename" << std::endl;
    fgets(buff, 4096, stdin);

    len = strlen(buff);
    if( buff[len-1] == '\n')
        len--;
    write(writefd, buff, len);

    while( (n = read(readfd, buff ,4096)) > 0)
    {
        std::cout << "the client read message from server:" <

有一个test文件 文件有一行数据this is a test

FIFO

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 


#define FIFO1 "/tmp/fifo1"
#define FIFO2 "/tmp/fifo2"

#define FILE_MODE   (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)

void client(int readfd, int writefd);
void server(int readfd, int writefd);

int main(int argc, char**argv)
{
    int readfd, writefd;
    pid_t childpid;

    if ((mkfifo(FIFO1, FILE_MODE) < 0) && (errno != EEXIST))  
        printf("can't create %s", FIFO1);  
    if ((mkfifo(FIFO2, FILE_MODE) < 0) && (errno != EEXIST)) {  
        unlink(FIFO1);  
        printf("can't create %s", FIFO2);  
    }  

    if ( (childpid = fork()) == 0) {        /* child */  
        readfd = open(FIFO1, O_RDONLY, 0);  
        writefd = open(FIFO2, O_WRONLY, 0);  

        server(readfd, writefd);  
        exit(0);  
    }  
        /* 4parent */  
    writefd = open(FIFO1, O_WRONLY, 0);  
    readfd = open(FIFO2, O_RDONLY, 0);  

    client(readfd, writefd);  

    waitpid(childpid, NULL, 0);     /* wait for child to terminate */  

    close(readfd);  
    close(writefd);  

    unlink(FIFO1);  
    unlink(FIFO2);  
    exit(0);  
}

void server(int readfd, int writefd)
{
    int fd;
    size_t n;
    char buff[4097];

    if( (n = read(readfd, buff, 4096)) == 0)
    {
        std::cout<< "read file error " << std::endl;
        return;
    }

    buff[n] = '\0';
    std::cout << "the server get filename from client:" << buff << std::endl;

    if( (fd = open(buff, O_RDONLY)) < 0)
    {
        std::cout << "the file file can't open file" << std::endl;  
        write(writefd, buff , n);
    }
    else
    {
        while( (n = read(fd, buff, 4096)) > 0)
        {
            std::cout << "the server read file:" << buff;
            write(writefd, buff , n);
        }

        close(fd);
    }
}

void client(int readfd, int writefd)
{
    size_t len;
    size_t n;

    char buff[4097];
    std::cout<< "pls input filename" << std::endl;
    fgets(buff, 4096, stdin);

    len = strlen(buff);
    if( buff[len-1] == '\n')
        len--;
    write(writefd, buff, len);

    while( (n = read(readfd, buff ,4096)) > 0)
    {
        std::cout << "the client read message from server:" <