pipe创建函数：
#include <unistd.h> /* Create a one-way communication channel (pipe).
If successful, two file descriptors are stored in PIPEDES;
bytes written on PIPEDES[1] can be read from PIPEDES[0].
Returns 0 if successful, -1 if not. */
int pipe (int __pipedes[]);
下面是一个测试实例，有些未说明函数,如Pipe，是pipe的一个包裹函数，二者参数及用法一致，仅仅是在包裹函数中添加了出错信息。
void client(int, int);
void server(int, int); int
main(int argc, char **argv)
{
int pipe1[], pipe2[];
pid_t childpid; Pipe(pipe1); /* create two pipes */
Pipe(pipe2); if ( (childpid = Fork()) == ) /* child */
{
Close(pipe1[]);
Close(pipe2[]); server(pipe1[], pipe2[]); // 子线程作为服务器端
exit();
}
/* 4parent */
Close(pipe1[]);
Close(pipe2[]); client(pipe2[], pipe1[]); Waitpid(childpid, NULL, ); /* wait for child to terminate */
exit();
}
/**
* 从客户端读取文件名，打开文件并将文件内容返回给客户端
* @param readfd 管道读描述符
* @param writefd 管道写描述符
*/
void server(int readfd, int writefd)
{
int fd;
ssize_t n;
char buff[MAXLINE + ]; /* 4read pathname from IPC channel */
if ( (n = Read(readfd, buff, MAXLINE)) == )
err_quit("end-of-file while reading pathname"); buff[n] = '\0'; /* null terminate pathname */ if ( (fd = open(buff, O_RDONLY)) < )
{
/* 4error: must tell client */
// 打开失败则直接将错误信息写入管道
snprintf(buff + n, sizeof(buff) - n, ": can't open, %s\n", strerror(errno));
n = strlen(buff);
Write(writefd, buff, n); }
else
{
/* 4open succeeded: copy file to IPC channel */
while ( (n = Read(fd, buff, MAXLINE)) > )
Write(writefd, buff, n);
Close(fd);
}
} /**
* 将键盘输入数据发送给服务器，并将服务器的回复信息显示在屏幕
* @param readfd 管道读描述符
* @param writefd 管道写描述符
*/
void client(int readfd, int writefd)
{
size_t len;
ssize_t n;
char buff[MAXLINE]; /* 4read pathname */
Fgets(buff, MAXLINE, stdin); // 从键盘获取输入信息
len = strlen(buff); /* fgets() guarantees null byte at end */
if (buff[len - ] == '\n')
len--; /* delete newline from fgets() */ /* 4write pathname to IPC channel */
Write(writefd, buff, len); // 写入管道 /* 4read from IPC, write to standard output */
while ( (n = Read(readfd, buff, MAXLINE)) > )
Write(STDOUT_FILENO, buff, n);
}
以上测试实例实现了一个如下的客户-服务器：