unix网络编程卷2：管道和FIFO

管道和FIFO

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。

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 <unistd.h>
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 <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <string.h>

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
= '\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:" <<buff;
}
}

有一个test文件 文件有一行数据this is a test

FIFO

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>

#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
= '\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:" <<buff;
}
}