基础知识：
管道是最初的Unix IPC形式，可追溯到1973年的Unix第3版。使用其应注意两点：
1）没有名字；
2）用于共同祖先间的进程通信；
3）读写操作用read和write函数
#include <unistd.h>
int pipe(int fildes[2]);
返回：成功返回1，否则返回-1.创建成功的两个文件描述符：f[0]和f[1]，前者用来打开读，后者用来打开写。#include <unistd.h>
ssize_t read(int fildes, void *buf, size_t nbyte);
ssize_t write(int fildes, const void *buf, size_t nbyte);
测试代码：
代码1
1 #include<stdio.h> 2 #include<unistd.h> 3 4 5 int main() 6 { 7 int n,fd[2]; // 这里的fd是文件描述符的数组，用于创建管道做准备的 8 pid_t pid; 9 char line[100]; 10 if(pipe(fd)<0) // 创建管道 11 printf("pipe create error/n"); 12 13 if((pid=fork())<0) //利用fork()创建新进程 14 printf("fork error/n"); 15 else if(pid>0) 16 { //这里是父进程，先关闭管道的读出端，然后在管道的写端写入“hello world" 17 close(fd[0]); 18 write(fd[1],"hello word/n",11); 19 } 20 else 21 { //这里是子进程，先关闭管道的写入端，然后在管道的读出端读出数据 22 close(fd[1]); 23 n= read(fd[0],line,100); 24 write(STDOUT_FILENO,line,n); 25 } 26 exit(0); 27 }
代码2
1 #include <unistd.h> 2 #include <stdio.h> 3 4 void client (int, int ) , server (int , int) ; 5 int main(int argc, char **argv) 6 { 7 int pipe1[2] ,pipe2[2]; 8 pid_t childpid; 9 10 pipe(pipe1);/* create two pipes */ 11 pipe(pipe2); 12 13 if ( (childpid = fork () ) == 0) 14 { /* child */ 15 close (pipe1[1]) ; 16 close (pipe2[0]) ; 17 server (pipe1[0],pipe2[1]) ; 18 exit (0) ; 19 } 20 /* parent */ 21 close (pipe1[0]) ; 22 close (pipe2[1]) ; 23 client (pipe2[0], pipe1[1]) ; 24 25 waitpid(childpid, NULL, 0); /* wait for child to terminate */ 26 exit(0) ; 27 28 } 29 30 31 void client(int readfd, int writefd) 32 { 33 size_t len; 34 ssize_t n; 35 char buff[MAXLINEI; 36 37 /* read pathname */ 38 fgets (buff, MAXLINE, stdin) ; 39 len = strlen(buf f) ; /* £gets() guarantees null byte at end */ 40 if (buff [len - 1] == ' ' ) 41 len--; /* delete newline from £gets() */ 42 43 /* write pathname to IPC channel */ 44 write(writefd, buff, len); 45 46 /* read from IPC, write to standard output */ 47 while ( (n = Read(readfd, buff, MAXLINE)) > 0) 48 write(STD0UT_FILENO, buff, n): 49 } 50 void server(int readfd, int writefd) 51 { 52 int fd; 53 ssize_t n; 54 char buff [MAXLINE + 1]; 55 56 /* read pathname from IPC channel */ 57 if ( (n = Read(readfd, buff, MAXLINE) ) == 0) 58 err-quit("end-of-file while reading pathname"): 59 buff[n] = ' '; /* null terminate pathname */ 60 61 if ( (fd = open(buff, O_RDONLY)) < 0) 62 { 63 /* error: must tell client */ 64 snprintf(buff + n, sizeof(buff) - n, ": can't open, %s",strerror(errn0)); 65 n = strlen(buf f) ; 66 write(writefd, buff, n) ; 67 } 68 else 69 { 70 /* open succeeded: copy file to IPC channel */ 71 while ( (n = Read(fd, buff, MAXLINE)) > 0) 72 write(writefd, buff, n); 73 close ( fd) ; 74 } 75 76 }
参考资料